While playing a game, type "cheatcheat" to enable cheat mode. Then, enter one of 
the following codes to activate the corresponding cheat function:

Result - Cheat Code
God mode - godmode 
Infinite ammunition - ammo 
Flight mode - fly 
Invisibility - invis 
Invincible enemies - hitlermode 
Win current mission - winmission 
Lose current mission - losemission 
Display debug information - stats