Directions:

Level select:
At the main menu, press R, L, Up, Down, X, Y, B.

Enter these codes while playing, without pressing pause:

Invincibility - R, L, Up, Down, A, R, L, Black, White
All Weapons - R, L, Up, Down, A, Up, X, A
Gravity - R, L, Up, Down, A, L, L
Lethal Charge - R, L, Up, Down, A, Black, Black
Punch Mode - R, L, Up, Down, A, Up, Up
Full Health - R, L, Up, Down, A, Up, Down
Bomb Mode - R, L, Up, Down, A, Up, White
SloMo Mode - R, L, Up, Down, A, Up, L
Megaforce - R, L, Up, Down, A, R, R
Nailgun Mode - R, L, Up, Down, A, White, White


Silenced Silverballers .45:
To get the Silenced Silverballers you have to get a Silent Assassin rank when you beat a mission.

Sawed-off shotgun:
Beat two missions with a Silent Assassin rank.

M4:
Beat the St. Petersburg missions with a Silent Assassin rank.