[F12]+[F1] - Restore Health
[F12]+[F2] - Get Shield
[F12]+[F3] - Get Ammo and Weapons
[F12]+[F4] - Win the Game
[F12]+[F5] - Get Fuel
Another way to get weapons, health, shield, and fuel is to hop on the back of a Pteranodon and ride him up high in the sky. At a certain altitude you will be given all the free stuff.
Double jump cheat
If you double jump off a mountain, you will get a shield and fuel.