If you're struggling and need a bit of help pause gameplay and press R2, Up, L2, Down, Left, Up, Left, Right, L2, R2 and you will get 99 lives.

During gameplay press pause and then enter R2, Down, L2, Up, Right, Down, Right, Left to receive 99 Explosive Bullets to use in the game.

Unlock Debug Mode:
During gameplay 'Pause' the game and hold L1 and quickly press Down, Down, Triangle.

Unlock Rear View Mirror:
During the Ski mini-game hold down L1 + R1.

Save a Life:
Before you are about to die when you fall of a cliff press 'Start' and exit the level and when you return to the level you will not have lost a life.