Cheats

Ingame press [^], and type in console in big letters...

SV_CHEAT_GODMODE_1 	Godmode
SV_MAX_AMMO_1 	        All Ammo
SV_EVERYTHING_1 	Max Health and Ammo
SV_DEMON_1 	        Demon Morph
SV_PERFECT_FINISH_1 	End Level