Level Select
Quickly press Square, Circle, R1, L1, L1 + R1 at the main menu.

All Weapons
Start a new game, then pause and press Square, Circle, R1, L1, R1+R2. You must enter the code within two seconds. NOTE: This code can be tricky, but it does work. We've confirmed it ourselves.

Run Faster in Multi-Player Mode
Hold Square + Triangle to chase your opponent quicker.

More Damage in Multiplayer
When using the flamethrower in two player mode, tap the X button instead of holding it. The flamethrower will then do more damage.

Secret Key
If you enter the two player level "Clean Up This Mess!," and go into the closet (located in the North East direction, you will find a key located between the books. Unfortunately, nobody seems to know what it is for.

Invincibility
during the game pause the game and press square, circle, L1, and then hold L1 and L2 together. but you must do this code under 2 secounds.

Secret level
When playing the game pause it and press Square 5 times with about a second between each square. When you unpause the game it will take you to one of three secret levels

Clear Mine Fields Quickly
When entering a mine field, select your minesweeper. Walk forward a few paces and then hold in the roll button and roll left/right to clear mines. This will save a considerable amount of time.