To activate Cheat Mode, push: up-C, left-C, down-C, right-C at the main menu. To enable the cheats, press Start and the following buttons:

Level Skip - C-Up, C-Down
Refill health - Z-trigger, R
Super-Breath - Z-trigger, L
Super-Speed and Flight - R, Z-trigger
Super-Strength - L, Z-trigger
X-Ray Vision - R, L