1 Shot Kills
This cheat will enable you to kill a person with one shot, even if they have a flak jacket. Pause the game, go to Weapons, highlight the silenced 9mm, and hold down left, L1, R2, select, Square, X. Gabe should say 'Understood'.
Submitted by Tim_Lassiter. 0% success rate. 

All Weapons
The following code will give you unlimited ammo for the weapons availible in the current level: Pause the game, highlight weapons, hold down R1, R2, Circle, X, Square. The Weapons screen should show all the availible weapons for that level.
Submitted by Tim_Lassiter. 0% success rate. 

Level Select
This code will give you access to all of the levels. Pause the game, go to the Options screen, highlight Level Select, then hold down left, L1, R1, Select, Square, X. A full list of levels should appear on the screen.
Submitted by Tim_Lassiter. 

Defeat Anton
To defeat Anton (the boss with the fire pack) all you need to do is shoot his fire pack with a M16 and don't run away until the danger bar moves half-way up the danger bar.
Submitted by Sam_Warwicker. 

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