Scientist.
Security Guard.
Headcrab.
Barnacle.
Zombie.
Houndeye.
Vortigaunt.
Bullsquid.
Soldier.
Tentacle.
Leech.
Gargantua.
Ichthyosaur.
Assassin.
Alien Grunt.
Apache.
Osprey.
Snark.
Alien Controller.
Gonarch.
Nihilanth.
Gordon Freeman.
The G-Man.
Gus.
