Max Steel

Enable cheat mode
Go to the title screen and press the following button combinations:
Hold Start and press Y, A, B, B, Y, A, X, B, X, B

Push X to bring up the stage selection screen and enter
the following codes:

All Weapons, health, ammo: During the gameplay, hold L + Start + A.
Invincibility: During the gameplay, hold L + Start + X.
Skip stage: During the gameplay, hold L + Start + Y.