Pause the game and enter the following codes.

Full health:
Left, Right, Left, Right, R1, L1, , , Down.

Invincible:
Up, Down, Right, Down, R1, R2, Down, , L1.

Enable Tube:
Up, Down, Left, Right, R2, L2, , Down, .

Switch to Equivalent Toon Version:
Up, Down, Up, Down, R1, R2, Down, , .

Give All Ups:
Left, Left, Up, Up, L1, R2, , Down, .

Give All Slams:
Right, Down, Up, Down, Down, R1, , , Down.

Infinite Reaver Charge:
Down, Down, Up, Left, R1, R2, Down, , .

All Dark Chronicles:
R1, Down, R2, L1, Right, R2, , Down, L1.

All Bonuses:
R2, Down, L2, R1, Left, L2, Down, L1, .

Wireframe:
L1, Down, L1, Up, R1, L2, L1, Down, .

No Textures:
L1, Down, R2, Right, R2, Up, , L1, Down.

Thanks to Revolution readers Paolo Augello and Kjell!