Full health gauge
Pause the game, then hold L1 + R1 (in order) and quickly press Right, Down, Left, Up. If you entered the code correctly, you will hear a sound.

Full Master Mode gauge
Pause the game, then hold L1 + R1 (in order) and quickly press Left, Down, Right, Up. If you entered the code correctly, you will hear a sound.

Health drops to 1 point
Pause the game, then hold L2 + R2 (in order) and quickly press Down, Up, Right, Left, Down, Up. If you entered the code correctly, you will hear a sound.

Master Mode gauge drops to 1 point
Pause the game, then hold L2 + R2 (in order) and quickly press Right, Left, Right, Left, Down(2). If you entered the code correctly, you will hear a sound.

Enemies shoot faster
Pause the game, then hold L2 + R2 (in order) and quickly press Right, Down, Left, Up. If you entered the code correctly, you will hear a sound.