Level skip
Press Start to pause game play, then press Up, Down, Left, Right(2), Left, Circle.

Level select
Save the game and return to the main menu. Select the "Resume Game" option, then highlight the previously saved game and press Up, Down(2), Up, Left, Up, Right, Down.

Invincibility
ress Start to pause game play, then press Square, Circle, Left, Right, Circle, Square. Alternately, press Start to pause game play, then press Square(2), Circle(2), Left, Right, Circle(2), Square(2).

Full ammunition
Press Start to pause game play, then press Left, Right, Circle(3), Right, Left.

All characters
Press Start to pause game play, then press Left(2), Circle(2), Right, Left, X.

All weapons
Press Start to pause game play, then press Left, Circle, Right, Square, Right, Left.

Fatboy Mutator
Press Circle(3), Up, Down(2), Up, Circle(3) at the main menu. Select multi-player mode and choose the Fatboy Mutator. Get killed to have the new Mutator get thinner. Get a kill to have the Mutator get bigger.

Stealth Mutator
Press Square(2), Circle(2), Square(2), Circle(2) at the main menu. Select multi-player mode and choose the Stealth Mutator.

Big head mode
Press Left, Right, Left, Right, Left, Right, Circle(3) at the main menu. Select multi-player mode, highlight the "Mutators" option and press X. Highlight the new "Big Head" option, then press Right, X.

Firewire multi-player mode
Note: This trick requires a four port Firewire PC hub. Use Firewire cables to connect the iLink port of one to three more PlayStation2 consoles to the hub. Press Start to pause game play in two player multi-player mode and press Left, Circle, Left, Right, Square, Right. Have all players press Start at the waiting screen.

USB multi-player mode
Note: This trick requires a USB keyboard and USB mouse. Change the controller configuration to set the keyboard to player three and the mouse to player four. The game can now by played with four players.