give monster_xxxxxxxxxx
[Replace x with the following:
alien_slave, alien_grunt, apache, barnacle, barney, barney_dead, bigmomma (gonarch), bullchicken, cockroach, furniture, flyer_flock, gargantua, generic, gman, grunt_repel, headcrab, hevsuit_dead, hgrunt_dead, human_grunt, human_assassin, houndeye, scientist, scientist_dead, sentry, miniturret, turret, ichthyasaur, leech, tentacle, zombie, hgrunt, nihalinth, osprey]
NOTE: You can only create a monster once you have actually seen it
/GOD God Mode
/NOCLIP Clipping On/Off
/Map c#a#? Go to Map xxxx, whereas # is a number and ? is either nothing or a letter
/GIVE xxxx Give Item xxxx. They're pretty obvious, such as item_antidote, ammo_9mmAR, ammo_9mmbox, weapon_9mmAR
sv_gravity # *Change Gravity to # (0-999)
Tip:
If you are having problems killing the monster in the Power Up stage, turn the track generator on then lure the monster into the generator room then run into the door then back out the other side the big dumb monster will die from electric shock.