Faster Tanks
From the Mode select screen, hold Z + R and press any C button.
(Thanks to feachured1999@hotmail.com)

Free Buildings
Press and hold Z at the menu and enter: A, B, A, B.
(Thanks to feachured1999@hotmail.com)

Free Satellite
Press and hold Z at the menu and enter: B, C-Left, C-Down, A.
(Thanks to feachured1999@hotmail.com)

Infinite Ammo
Press and hold Z at the menu and enter: L, R, L, R.
(Thanks to feachured1999@hotmail.com)

Infinite Armor
Press and hold Z at the menu and enter: Up, Right, Down, Left.
(Thanks to feachured1999@hotmail.com)

Unlock all Levels
Press and hold Z at the menu and enter: C-Up, C-Right, C-Down, C-Left, Start.
(Thanks to feachured1999@hotmail.com)