While playing, press ' or ; to bring up the console. Enter any of the following codes with a forward slash in front of them.

Example: /godmode

Code - Effect

ac - God Mode, Unlimited Ammo, Fly Mode
arrival - Render Arrival Points
ammo - Unlimited Ammo
cheatcheat - Enable All Cheats
ec - Follow Mode
fovs - Render Enemy FOV's
give # - Give Item #
fly - Fly Mode
godmode - God Mode
hitlermode - Hitler Mode
invis - Invisibility
losemission - Lose Mission
pathdraw - Render Patrol Paths
tod # - Change Time of Day (1-5)
winmission - Win Mission