Cheat Mode
In game hit "Pause" key, jump to "Mission Objectives" screen (without grey buttons on top) and then type in the codes. You can also bring the command line by pressing the Global Chat key and type the codes there. In this case you need to put slash character in front of a cheat, example /cheatcheat.
cheatcheat - Enable Cheat Codes
godmode - God Mode
losemission - Lose Mission
winmission - Win Mission
hitlermode - Hitler Mode (Enemies Don't Die) On/Off
ammo - Unlimited Ammo
fly - Fly Mode
invis - Invisibility
ac919 - God Mode + Unlimited Ammo + Fly Mode On
ec919 - Enemy View
noint919 - Status Bars Visible On/Off
stats - Show FPS, Polygons, Sound.. On/Off
fovs919 - Rendering Enemy Fovs On/Off
pathdraw919 - Rendering Paths On/Off
wpdraw919 - Rendering Waypoints On/Off
wpcondraw919 - Rendering Waypoints Connections On/Off