Cheat mode:
Press [Tab] during game play and select the computer.
Type g0 ([g] and [zero]) and tpye the codes below:

Code - Result
4003 - full health
0038 - you are always silently
4828 - all other things
5332 - god
9123 - quick computer scanning
2354 - you make more health damage
8216 - more health
2352 - all weapons
4616 - 100% accuracy
6235 - first-aid kits are 2x more powerfull
2695 - infinite ammo
4982 - no one can hear you
8892 - no one can see you