Debug mode Pause game play, then hold L1 and quickly press Down(2), Triangle.
Keep current lives
Press Start and select the "Exit" option after falling. The game will begin again at Time Station with the same amount of lives.
Collect more explosive bullets
Pause the game and press R2, Down, L2, Up, Right, Down, Right, Left to collect up to 99 explosive bullets. Usually the game limits you to collecting a maximum of nine explosive (flash) bullets for the sling back shooter (sling shot). After entering this code you can exceed this limit. The game will not automatically give you more bullets, you must collect them yourself.