This weird little creature is the first enemy you'll encounter. It looks like a four-legged spider only it has a relatively large body. It's very slow, and won't notice you if you're more than 30 feet away from it, but if you get within 10 feet, it'll jump you. It jumps very fast, and the only way to avoid it is to make a very quick side-step. After having attacked you it'll pause for about two seconds, then attack again if you're within range. These guys can give you a real shock if you are unaware of their presence, but most of the time you'll see them before they're close enough to attack you, so generally they shouldn't cause too much trouble. The best weapon against them is one of the most basic one you have, the glock. Three shots will always bring them down, and since the glock is a very accurate weapon, you'll have no trouble killing them. Any other weapon is actually too powerful too waste on it, if you're in a hurry you can use the MP5, but you'll more than often end up spending up to five or six bullets on it, so I recommend that you just take your time, aim with the glock, and....pow, pow, pow...it's dead.
Attack: 5/10/10 per bite
This is the second enemy you'll face in Half-Life, and it has long arms and fingers, and is pretty slow. If you let them get too close, they'll try to hit you with their arms, which can actually hurt quite a bit if you've got no armor to protect you, so be careful. When you first meet them, you'll only have the crowbar and the glock, and although you'll probably face some fair amount of ammo problems in the beginning of the game, I would suggest using the glock. It takes ten hits with the crowbar, and you're very vulnerable to their arm attacks. Five direct hits in the head with the glock will make them shake and fall dead to the ground. The best weapon against them, if you've got it, is the shotgun. Two shots in the head will always kill them if you're not too far away. You'll only see these guys early in the game, so you won't have much of a chance to use other weapons against them, they're also too weak for that, so stay with the shotgun and you'll be fine.
Attack: 10/20/20 per single-slash
Attack: 25/40/40 per double-slash
These noisy beasts are one of the easiest enemies to kill in Half-Life. They run around "squeaking" all the time, and actually sound and look rather cute. When they come within range of you they stop and start charging up their weapon, which takes so long time (more than 2 seconds) that you should be either stuck or be an idiot to get hit. When they fire they send beams of energy out in circles from them, beware; this can set of explosives and trip mines for instance. This will hurt you a bit, and as they're often seen in large groups, you should be prepared to hide from their beams. As said, these guys aren't really the toughest of them all, so I recommend using the shotgun, one shot at point-blank range will kill them. The glock is useful too, 4 shots and they're dead. If you don't want to waste time switching weapons, the MP5 can be used too, its rapid fire can quickly get rid of large groups of them. If you face many of them, a well placed hand grenade, satchel charge or trip mine is also very good, especially because of the extreme joy it usually brings up in a player, setting a nice little satchel charge off like that, repainting the walls with blood. You should be careful when using the trip mines, remembering that their attack can set it off. You shouldn't waste larger weapons on them.
Attack: 10/15/15 per blast
These dudes are used as workers around the galaxy, you'll sometimes see them work in mines or other places. It's fun to watch them work as they run around, talk to each other and operate various machinery. They can run pretty fast, and are good at hiding from you. Their weapon consists of firing green electric beams at you. When they spot you, they'll run towards you until they are within range (they can fire from as far as about 100 feet), they'll then stop and start charging up their weapon. They do this by "sucking" energy off the floor and surrounding walls, you'll see green beams coming out of them. They do this for about a second (takes 2 seconds on easier skill levels), then fire a hitscan green ray of electricity towards you. They will always hit you no matter how fast you are running or how much you are jumping, so your only hope is to hide behind something. They have another way of attacking, which is by slapping you in the face if you get too close. It's easy to avoid their greasy hands if you quickly pull backwards, so you shouldn't allow them to hit you. You will however want to kill them, and this is best done with the MP5 or the shotgun. Two direct buckshots will kill them, more than three shouldn't be needed. The MP5 will get them down even quicker. The reason for their weakness is that they can actually pack quite a punch with their electric beams, and, considering the fact that they're often seen in groups of up to four, it's only reasonable that they're not stronger than they are. These guys will chase you throughout the game, you'll even have to deal with them in the very last levels of the game. At that point they are often so numerous, that it might be easiest to use the magnum, two shots will kill them (one headshot). The last few levels are by the way often so vast that you can easily take time to snipe them from far distances. They are also called Vortiguants.
Attack: 25/25/25 per slash
Attack: 10/10/15 per zap (sometimes up to 50 actually, it's a bit hard to say)
You'll find these things stuck to the ceiling, with their long tongue hanging down from them. They are actually really easy to see, and therefore you won't get caught unless you aren't very cautious. When you get too close to their tongue, you'll be slowly pulled towards their bodies, then bitten and thrown on to the floor. It'll die by biting you, just like a bee dies after having stung you. The bite hurts a lot
, and you might fall so far that you could crater from it so you must kill it fast, once you've been pulled in. I suggest that you use the weapon you have currently selected, however, most of the time you'll probably see it without being pulled in, and the easiest way to kill it then would be with a shotgun. One or two shots from a not-too-far distance should kill it, and since the shotgun isn't very useful later on in the game and against bigger enemies, it doesn't matter whether you waste a bit of ammo. A couple shots from the glock will also kill them, and so will one whack from the crowbar, how strange it might seen. They can actually be useful too, given their relaxed nature and passive attack. You'll sometimes find them besides a platform that you won't be able to reach by jumping. You can then let yourself be trapped by the barnacle, get as close to the ceiling as possible, kill it, and then jump on to the platform from there. This requires some training. I haven't really figured out exactly how this thing deals damage, but if you've got less than a 100 health and get bitten, you're dead. The thing is, that when you're bitten at first it'll pause for about 5 seconds, then bite you again, and again if you're still alive.
Attack: A lot of damage per bite - three bites will kill you no matter what
While the name might suggest otherwise, these things have nothing to do with bulls. Actually they're more like pigs, but I'll get back to that. They can move quite fast, but you'll mostly see them just standing there without moving, as they spit neon-green colored slime balls at you. They aren't very accurate shooters, and if you're far away from them, they probably won't hit you at all. If you get too close to one of these suckers, you will hear them grunting in a very pig-like way, and then see yourself being slapped 15 feet backwards, taking a fair amount of damage. In rare situations, they can also whip you with their tail. This can kill you quite fast, and you should not let this happen. When it comes to killing them, many of the more powerful weapons will work. The magnum will do the job magnificently, a couple of .357 rounds will make them fall flat on their stomachs. The MP5 can be used too, circle strafe it while you shoot, and it should be dead in not-too long. If you intend to use the shotgun, use the alt-fire, and be prepared to spend at least 2x2 shells on it. If you feel you've got enough ammo, the crossbow will work too. You should note that they for some reason are three times stronger on difficult than on easy and medium, so you can safely rely on weaker weapons when playing on those skill levels.
Attack: 15/25/25 per bite
Attack: 10/10/15 per spit
Attack: 25/35/35 per tail-whip
A very rare enemy, you won't meet more than seven of them throughout the game, two times in groups of two or three, and two of them are alone. They have a long, green body and a huge blade at the end of their heads. If you get hit by this thing, you'll be seriously hurt, even if you only brush it. They're sort-of like the worms from the movie "Tremors", they can only see things that move, and have an ear on each side of their heads so that they can locate you. This means that you have to walk slowly past them if you don't want to get chopped. If you dare, you can distract them by firing a grenade somewhere, they'll go nuts at the spot it exploded. These are one of the only enemies in Half-Life that cannot be killed, no matter how much you try, it wont help. You can, however, make them leave you alone for a few seconds if you give them a shot with the shotgun or another weapon. Be careful that you don't get "stuck" to their bodies if you get too close (it's possible).
Attack: Up to ~100 per slash
This monstrous creature (Garg) is not seen very often, and thank God for that. He can't really be considered a boss, since you'll see him 4-5 times throughout the game. He has two giant flamethrowers mounted on each arm, and if you get within about 20 feet of him, he'll start frying your ass, so be careful. He also sometimes stomps in the floor, which sends a slow moving, red thing towards you, soaring above the ground. This is extremely easy to dodge, so don't let yourself get hit by this. If you get too close, he can whack you with his hands, which makes your view tilt about 40 degrees, making it very hard to see where you are. I'd estimate his height to about 15 feet, and he may seem impossible to kill. Well, one of the coolest things about Half-Life is the fact that almost every enemy can be killed/destroyed no matter how big they are, which means that it is possible to kill him. There is one catch though; He can only be hurt by using explosives, this is probably because of his body armor. The first time you'll meet him is at "Power Up", where the only explosives you can possibly have will be max. 10 hand grenades and a couple of trip mines, which will just about do the trick. Other things that can kill him are 7+ satchel charges, 10 RPG's, 10 MP5 grenades or 72 egon cells. Of course you can't carry 10 RPG's with you, so if you want to use them, shoot him in the head, 5-6 will kill him then.
Attack: 3/5/5 per round
Attack: 10/30/30 per slash
Attack: 50/100/100 per stomp-fire
These giant fish-like things are not nice to meet. When they spot you under water, they'll swim fast towards you, and occasionally bite you, which really
hurts, so be careful. When you get bitten, your view will become seriously distorted, making it very difficult for you to navigate. Three-four bites can kill you, so you do not want to stay near these. They are very hard to kill, but luckily it often won't be necessary to do so. First of all, it is nearly impossible to hit it with a weapon that can't be fired under water, and any weapon that need to be thrown or put somewhere is useless, because the fish moves around a lot. That leaves us only with a couple of weapons, for instance the RPGL, you can fire them under water, and they can be guided for maximum precision. Stay as far away from it as you possibly can, be sure to maintain your breadth of view, and fire four RPG's at it, that'll kill it. The crossbow is also a bit useful, 8 shots will kill it, but arrows act very weird under water, so you probably won't hit anything.
Attack: 20/35/50 per bite
These little annoying creatures are extremely rare. You've probably encountered them once in a while in death match, where you can irritate your opponents by throwing them in their heads, but they aren't very useful in single player. They are, besides being a weapon, also an enemy, and if you don't remain calm, groups of these tend to overwhelm you. They are very fast, making it difficult for you to aim at them, and they'll keep attacking you until they explode after 15 seconds. The best weapon against them is the MP5, considering it's rapid fire and tiny spread. You are best off by running backwards while firing at them, as it might take a while for you to hit them.
Attack: 10/10/10 per bite
Attack: 5/5/5 from explosion
These are one of the toughest, most intelligent aliens you'll meet, and you should be careful not to walk right into them. They're as tall as you, but about three times wider. They're heavily armored, and have a hornet gun which they use to fire heet seeking hornets at you. They're no faster than you are, so if he starts firing at you, run as fast as you can in the opposite direction, as the flies can only follow you for about a 100 feet, they'll then disappear. If you get too close of these, they'll smack you with their big hands, so keep a distance. You shouldn't be afraid to use a powerful weapon against them. The magnum or crossbow will kill it with 3 shots, but you've got to be quick, be sure to have reloaded them before you walk into battle. The tau cannon is useful against them, one charged alt-fire shot will gib them. If you want to use the gluon gun, you should be prepared to lose some energy, as it takes some time for it to gib them. The MP5 is very useful, one well-placed grenade plus a few rounds should kill them. They generally don't move around a lot, so aiming at them shouldn't be a problem. They have armor on their shoulders that protects them from projectiles.
Attack: 10/20/20 per slash
Attack: 4/5/8 per hornet
You won't see these flying bastards until the last part of Half-Life. They have a huge head, and fly pretty fast trough space. They fire yellow balls of energy at you, up to 10 at a time, sometimes only a couple. They are often seen in groups, which makes it necessary to kill them fast. The best weapon to bring these down with is clearly the magnum. It has hitscan projectiles, and three shots will kill them. Two crossbow shots will do the same, but the problem is that the arrows are somewhat slow, and since these aliens move around a lot, you'll often miss them. However, if you think you are in a safe position, you can wait a while to find out in which pattern it is moving, and then fire your arrows in correspondence to that. If you feel you need to get rid of them quick, the gluon gun is not too powerful. I feel the tau cannon is kind of hard to hit a moving target with, and you'll probably end up wasting all your ammo. The hornet gun is great for killing these things, hide somewhere, let the gun recharge, then get out and fire the hornets at them. The RPGL is pretty useless against them, you'll miss them for sure if you use it. Their weapon doesn't deal that much damage, the projectiles are slow, and you shouldn't worry too much about them. If you however bumb into hordes of them (as you can sometimes do on the final levels) while in a cramped little room, it's time to panic. Move around as fast as you can, use the magnum for a start, and if you can hide, start using the hornet gun.
Attack: 3/4/5 per energy ball
You will find these "plants" on the later levels, where they will stand at random spots, waiting for something to come by. When you get too close to its tentacle it'll whack you approximately each second if you don't get out of the way. This can be painful if you let it happen too many times, so watch out. You can easily sneak past it by walking, it won't notice you then. Crouch-walk if you have "always run" turned on. They cannot be killed.
Attack: 10 per whack
Gonarch, AKA "Big Momma"
Wow, this thing is big! You'll only meet her once in the entire game, on one of the final levels in the Alien World. It's about three times taller than you, has four big legs, and a huge sack hanging from its body. It can whack you if you get too close. It constantly spews out pods of acid with baby Gonarchs in them who will jump you when get within range. They will first eat up your armor, one armor point at a time, then your health. This might sound ridiculous, but they are often so numerous that they can get you trapped, leaving you no chance. Also, because they're so small and almost transparent, they're almost impossible to hit, so use the hornet gun, that way you don't have to aim that much. The only way to kill her is to just keep shooting the big egg-sack hanging underneath her until she eventually falls to the ground, dead. In these situations you should always use your most powerful weapons first, so start with the gluon gun. Then use your RPG launcher, MP5 grenades, magnum, crossbow and so on. Take note that the baby Gonarchs don't die because she does.
Health Factor: 1x/1.5x/2x - how many times more damage she needs to start running away/dying etc.
Attack: 50/60/70 per whack
As described above.
Attack: 2/2/2 per bite
The final monster of Half-Life. This thing is HUGE, and it soars in the middle of an enormous cave with a zillion feet to the roof. It has two ways of attacking you, where one of them is really a defense. First, it can shoot a pack of about ten white/blue balls of energy at you. If you just stand there, you'll be killed for sure, so if you can't hide, at least try to avoid them in some way. They have splash damage, so you better stay as far away from them as you can. The second thing he can do is the send a green teleport ball towards you, this will home in on you, and then send you to another place. You can either hide in some way that will make the ball hit a rock (remember, that if the rock is thin enough, you'll still be teleported), or you can fire a projectile of some kind into it which will make it disappear. This can't be a bullet or an energy beam, so use an arrow instead, it's a shame to waste a grenade or an RPG on it. He gets his energy from some orange-colored crystals hanging in the cave, so the first thing you should do is to shoot them. Three-four magnum or crossbow shots will do the trick. When you've done that you won't really see anything change, but that's because he still has a crystal inside his head. Just keep shooting him in the head, use your most powerful weapons. You'll notice that he soon starts to sound weakened and only fire one energy ball at a time, this means that he's almost dead. Keep shooting, and he'll die in a gigantic blast of colored beams and rays.
Attack: 30/30/50 per energyball