At the "Press Start" screen, hold L1 + L2 + R1 + R2 and use these codes to get the following effects:
Infinite health: Up, Right, Down, Left, Up, Left, Down, Right.
Infinite combo meter: Left, Right, Up, Down, Right, Left, Down, Up.
All upgrades: Up(2), Left(2), Right(2), Down(2).
All bonuses: Down, Up, Down, Up, Left, Right, Left, Right.
Dark Knight difficulty setting: Down, Left, Right, Up(2), Right, Left, Down.