While playing, press [~] (tilde) to bring up the console, then type any of the following codes:
Note: Cheats are active only in Daydream and Insomnia difficulty modes.

Code - Result:
PKGOD - God Mode
PKDEMON - Demon Morph
PKWEAKENEMIES - Weak Enemies
PKALWAYSGIB - Excessive Gibbage
WEAPONSPECULAR 1 - Weapon Specular On
PKWEAPONS - All Weapons
PKAMMO - All Ammo
PKHEALTH - Full Health
PKPOWER - Full Ammo and Health
PKGOLD - Add Gold
PKHASTE - Haste
PKWEAPONMODIFIER - Weapon Modifier Mode
PKKEEPDECALS - Decals Never Disappear
PKKEEPBODIES - Bodies Never Disappear
PKCARDS - Unknown Effect

Other Console Commands:

JOIN
SPEEDMETER
CROSSHAIR
FRAGLIMIT
CAMERAINTERPOLATION
PLAYERPREDICTION
MSMOOTH
ROT
TIMELIMIT
NETSTATS
NOTREADY
POS
MAP
READY
HUDSIZE
BREAK
DEMO
STRESSTEST
SHOWWEAPON
UPDATEPARAMS_PHYSICSITEMS
UPDATEPARAMS_PLAYERS
UPDATEPARAMS_MYPLAYER
UPDATEPARAMS_PROJECTILES
SERVER
FOV
ACTIONSENDPERIOD
MSENSITIVITY
NAME
TEAM
MAXPACKETSIZE
EXIT
QUIT