Half Life - Part 3

Continuing with the theme of enemies, the next one on the list and probably the most terrifying of them all, is the Ichthyosaur. This underwater monster has massive teeth, claws instead of fins even though it resembles a fish and what makes it terrifying is that you don't know it's there before it hits you. Unless of course you know where to expect it. It can tear Gordon to shreds in quite a short time, so it's best avoided or if you can, killed quickly.
Preferred Weapon: Crossbow. The only other weapon that works underwater is your 9mm sidearm and it really isn't very effective in this case. If you can get a shot from above water though, you can use any powerful weapon at your disposal.

The Alien Grunt is the next new enemy you'll encounter. This bruiser looks like some kind of mutated gorilla and is best confronted from a distance, with a powerful weapon. It shoots small wasp-like creatures from its alien "sidearm" and it packs a mean punch in close quarters.
Preferred Weapon: Close range; shotgun. Long range; .357magnum.

Enemies you won't encounter often in the game are the so-called Snarks. These odd creatures resemble a headcrab, but are ten times faster and can leap an incredible height. They're usually found in nests which should preferably be left alone. They aren't very tough; like with a headcrab one or two shots even from the smallest weapon you have will take them down, but they do quite a bit of damage in attacks and since they usually attack in groups, this could prove fatal if you're not careful. The player has access to them as weapons late in the game, although after being released they attack anything in the vicinity, you included if there aren't other enemies nearby. If shot, they explode into a gooey puff that also does some damage. This also happens after a period of time even if they aren't attacked. Not the best way to go, really.
Preferred Weapon: Anything that shoots. You don't want to use the crowbar on these things...

An enemy you'll almost solely encounter on the border world of Xen is the Xen Master. These flying creatures have a large head and small torso with relatively small arms and legs. They shoot what looks like fireballs when they notice an enemy. They're relatively easy to kill, but persistent, especially in the last level of the game.
Preferred Weapon: Anything long-range.

Gonarch. Ugh. This spider-like monstrosity seems to be the source of all the headcrabs you fight on Earth. It's one tough cookie and you'd do best not to engage in close combat. It shoots strange, poisonous projectiles at you, as well as releasing hatchling headcrabs. These don't do much damage, so they should be dealt with when you get the chance, rather than focusing on them. You will be chasing Gonarch across several levels, which makes her one of the strongest enemies in the game. She can be hurt by aiming at the sac that looks like her abdomen.
Preferred Weapon: Anything that shoots. You're going to need a LOT of bullets etc. for this one...

The last enemy you'll face in the game is called the Nihilanth. It looks like a floating baby with claws and shoots what seems to be energy projectiles at you. This creature is responsible for all the chaos on earth. It's immensely powerful and some of its energy projectiles (the green ones) can teleport you to other levels. It also teleports other enemies into the chamber that makes it more difficult to kill the Nihilanth itself.

Next, in Half Life - Part 4: The Military Assault on Black Mesa