Cheat Mode:
During the game, press [TAB] to open the inventar. Choose the PDA and start it with [E]. Now press the keys [G] + [0] together.

Code - Result:
3815 - Unlimited Health
8745 - Full Health
0132 - Medi-Kits Double Effect
6422 - Double Protection
7663 - Double Damage
7018 - All Items
8700 - All Weapons
8249 - Unlimited
4394 - 100% Aiming
6467 - Faster Hacking
2733 - Enemies are Blind
1554 - Enemies are Deaf
0926 - Moving Without Noise