Various Cheats:
Patch the game before using these

Start your game with the -debug command line parameter. To do this edit your properties to read avp.exe -debug

Enter the cheat console by pressing ~ + [F12] then enter these codes when using the character listed

effect/characteruse/code

Create CPU controlled Alien Any alienbot
All weapons and ammo Any giveallweapons
God mode Any god
Create light aura; repeat for brighter aura Any light
Create an CPU controlled Marine Any marinebot <class number>
Player invisible to all opponents Any observer
Create CPU controlled Predator1 Any predobot <class number>
Create CPU controlled Predator-Alien1 Any predalienbot
Create CPU controlled Praetorian Alien1 Any praetorianbot
Create CPU controlled Xenoborg1 Any xenoborg
Display level coordinates Any showcoords
Display frame rate Any showfps
Display number of rendered polygons Any showpolycount
Replenish energy supply Predator gimme_charge
God mode Marine freakoftheunivers
God mode Predator skullcollector
God mode Alien theonedeadlycreautureevercreated
Become Final Xenomorph Alien winneroftheonegreatbattleoftheuniverse
List in-game help Any listvar
List cheat commands Any listcmd
Change motion tracker volume Marine motiontrackervolume <0.00-1.00>
Change motion tracker speed Marine motiontrackerspeed <0-16>
Toggle crouch and crawl Alien crouchmode <0 or 1>
Change game speed Any timescale <0.0-1.0>
Toggle wire frame mode Any wireframemode <0 or 1>
Toggle doppler shift on Alien sounds Any dopplershift <0 or 1>
Adjust amount of red in sky Any sky_red <number>
Adjust amount of green in sky Any sky_green <number>
Adjust amount of blue in sky Any sky_blue <number>
Adjust amount of tilt when sidestepping Any leanscale <number>