Cheat List
Enter the following during the middle of gameplay:
TRIANGLE, X, SQUARE, CIRCLE, CIRCLE, UP - shotgun
TRIANGLE, X, SQUARE, CIRCLE, CIRCLE, LEFT - invisibility
TRIANGLE, X, SQUARE, CIRCLE, CIRCLE, RIGHT - slow motion
TRIANGLE, X, SQUARE, CIRCLE, CIRCLE, DOWN - fast motion
TRIANGLE, X, SQUARE, CIRCLE, X, UP - change spawn point
TRIANGLE, X, SQUARE, CIRCLE, X, RIGHT - infinite ammo
TRIANGLE, X, SQUARE, CIRCLE, X, DOWN - max charisma
TRIANGLE, X, SQUARE, CIRCLE, X, LEFT - nail gun
TRIANGLE, X, SQUARE, CIRCLE, TRIANGLE, UP - sub machine gun
TRIANGLE, X, SQUARE, CIRCLE, TRIANGLE, RIGHT - sniper rifle
TRIANGLE, X, SQUARE, CIRCLE, TRIANGLE, LEFT - rocket launcher
TRIANGLE, X, SQUARE, CIRCLE, TRIANGLE, DOWN - heavy machine gun
TRIANGLE, X, SQUARE, CIRCLE, SQUARE, UP - ragdolls

Unlock Liberty Island
To unlock the extra stage, Liberty Island, just beat the game on any difficulty