Press ~ to display the console window, then enter one of the following codes. 

PKGOD - toggle 'godmode' on/off 
PKDEMON - toggle 'demon morph' on/off 
PKWEAKENEMIES - toggle 'enemies get 1 hp' on/off 
PKALWAYSGIB - toggle 'excessive gibbage' on/off 
WEAPONSPECULAR 1/0 - toggles 'weapon specular' on/off 
PKWEAPONS - gives all weapons 
PKAMMO - full ammo 
PKHEALTH - full health 
PKPOWER - full ammo/health 
PKGOLD - lots of gold 
PKHASTE - toggle haste on/off 
PKWEAPONMODIFIER - toggle 'weapon modifier mode' on/off 
PKKEEPDECALS - toggle 'decals will never disappear' on/off 
PKKEEPBODIES - toggle 'bodies will never disappear' on/off

Console Commands:
Enter debug mode and type one of the following console commands. Some of these commands are flags, as in they must be followed with a 0 or 1. 

NAME 
GOD 
GIVEALL 
EXIT 
SHOWWEAPON 
SERVER 
FOV 
MSENSITIVITY 
MAP 
JOIN 
MSMOOTH 
TPP 
PLAYERPREDICTION 
CAMERAINTERPOLATION 
HUDSIZE 
QUIT 
FRAGLIMIT 
CROSSHAIR 
TIMELIMIT 
SPEEDMETER 
BULLETTIME 
POS 
ROT 
DIDELTASCALE 
WEAPONSPECULAR 
USEDINPUT