While playing the game, press X, B, X, B, UP, UP, DOWN, DOWN.

Enter these codes while playing. The cheat effects last for the stage, so if you load a game or load a new map (i.e., go into the next stage), enter the cheat again.

99 COnviction - Y, Y, Y, Y, UP, DOWN, UP, DOWN
Infinite Ammo - X, X, X, X, UP, UP, DOWN, DOWN
God Mode - R, R, A, A, UP, DOWN, UP, DOWN
All Weapons - A, A, A, A, UP, DOWN, UP, DOWN
Weapons Do Insane Damage - B, B, B, B, UP, DOWN, UP, DOWN
All Special Weapons - B, A, B, A, B, A, BLACK, WHITE
Restock Ammo For Selected Weapon - A, B, WHITE, BLACK, B
Melee Attacks Do More Damage - X, X, Y, Y, UP, DOWN, UP, DOWN
Earn All Edges - Y, Y, UP, DOWN, UP, DOWN
Edges Use Zero Conviction - L, L, A, A, UP, DOWN, UP, DOWN
Skip Level - BLACK, L, BLACK, L, UP, DOWN, UP, DOWN
Restore Health - B, B, WHITE, WHITE, WHITE
Play Nightmare Difficulty - BLACK, BLACK, UP, UP, DOWN, DOWN

Submitted by - thyrobster and elvencroft