Complete Level:
During gameplay, press R2, L2, UP, DOWN, X, L3, CIRCLE, X, CIRCLE, X.

Cheat List:
Enter these codes during gameplay:
Slow motion - R2, L2, Up , DOWN, X, UP, L2
Full Heal - R2, L2, UP, DOWN, X, UP, DOWN
Punch Mode - R2, L2, UP, DOWN, X, UP, UP
Gravity - R2, L2, UP, DOWN, X, L2, L2
Lethal Charge - R2, L2, UP, DOWN, X, R1, R1
Bomb Mode - R2, L2, UP, DOWN, X, UP, L1
Megaforce - R2, L2, UP, DOWN, X, R2,R2 (restart level to remove effects)
Nailgun Mode - R2, L2, UP, DOWN, X, L1, L1
Level Menu (activated at main menu) - R2, L2, UP, DOWN, SQUARE, TRIANGLE, CIRCLE

Level Select, All Weapons, and Invincibility:
Level Select: At main menu enter: R2, L2, UP, DOWN, SQUARE, TRIANGLE, CIRCLE

All Weapons:
While playing a game enter: R2, L2, UP, DOWN, X, UP, SQUARE, X

Invincibilty:
Enter this code while playing a game, R2, L2, UP, DOWN, X, R2, L2, R1, L1

Unlock Sawed-off Shotgun:
To unlock the sawed-off, beat any two missions with a Silent Assassin ranking.

Unlock Silenced Ballers:
To unlock the Silenced Ballers, get a Silent Assassin ranking on any mission.

Unlock the M4:
Earn a Silent Assasin ranking on the St. Petersburg missions. Once you complete "Invitation to a Party", you unlock the M4.