Pause the game and enter the codes during gameplay. A voice byte will play if the code was accepted.

All weapons - UP, DOWN, LEFT, RIGHT, LEFT, RIGHT, LEFT, LEFT
Inf ammo - UP, DOWN, LEFT, RIGHT, UP, LEFT, DOWN, RIGHT
Inf Necroplasm - UP, DOWN, LEFT, RIGHT, DOWN, LEFT, UP, RIGHT
No blood - UP, DOWN, LEFT, RIGHT, UP, UP, UP, UP.
Unlock all comics - UP, DOWN, LEFT, RIGHT, RIGHT, LEFT, LEFT, UP.
All missions - UP, DOWN, LEFT, RIGHT, LEFT, LEFT, RIGHT, RIGHT.
Encyclopedia - UP, DOWN, LEFT, RIGHT, LEFT,RIGHT, UP, DOWN.