Trial mode
At the "Press Start" screen, quickly press Up, Down(2), Right(3), Left(4), then hold Triangle and press Start to unlock trial mode. If you entered the code correctly, you will hear the sound of a gunshot. This mode allows any level in the game to be played. Note: The code must be entered before demonstration mode begins.

Sudden death mode
At the "Press Start" screen, quickly press L2, R2, L2, R2, Circle, Triangle, Circle, Triangle, then hold L1 and press Start to unlock sudden death mode. If you entered the code correctly, you will hear the sound of a gunshot. This mode allows opponents and your character to be killed with one hit. Note: The code must be entered before demonstration mode begins.

Max power mode
At the "Press Start" screen, quickly press L1, R2, L2, R2, L2, Triangle, Circle, Triangle, Circle, then hold L1 and press Start to unlock max power mode. If you entered the code correctly, you will hear the sound of a gunshot. This mode allows you to start with all weapons and infinite ammunition. Note: The code must be entered before demonstration mode begins.

All multi-player characters
At the "Press Start" screen, quickly press Up, Down(2), Right(3), Left(4), then hold Circle and press Start to unlock all the Bosses as well as the engineers and a few army characters in multi-player mode. If you entered the code correctly, you will hear the sound of a gunshot. Most of the Bosses have odd guns and may not be able to back up against walls or roll. Alternatively, successfully complete the game on the easy and normal difficulty settings. Note: The code must be entered before demonstration mode begins.

Max power, sudden death, trial modes
Successfully complete the game on the hard difficulty setting to unlock max power, sudden death, and trial modes.