Hard Difficulty - Finish all levels on NORMAL.
Infinite Ammo Cheat - Finish all levels on NORMAL with an A grade.
Infinite Shield Cheat - Finish all levels on HARD.
Infinite Health Cheat - Finish all levels on HARD with a C or above.
Infinite Grenades Cheat - Finish all levels on HARD with a B or above.
Choice of Left Hand Weapon - Finish all levels on HARD with an A.