At the "Press Start" screen, quickly press Up, Down(2), Right(3), Left(4), then hold C-Down 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. -From: KiddReign2@aol.com

At the "Press Start" screen, quickly press C-Left, C-Right, C-Left, C-Right, C-Up, C-Down, C-Up, C-Down, then hold L 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. -From: golf_freak99@hotmail.com

At the "Press Start" screen, quickly press L, C-Right, C-Left, C-Right, C-Left, C-Down, C-Up, C-Down, C-Up, then hold L 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. -From: JRDINODR@aol.com

At the "Press Start" screen, quickly press Up, Down(2), Right(3), Left(4), then hold C-Up and press Start to unlock all the Bosses as well as the engineer 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.

When out of pistol ammunition in story mode, press B to reload.

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

Wait for demonstration mode to begin at the "Press Start" screen. Eventually, another sequence will appear after memo mode cycles a few times.