Contra Rebirth Cheats

Unlockable characters and difficulties
When you beat the game on a set difficulty, you will be able to unlock new secrets. The characters in the game are Tsugu-Min (a female android) and Plisskin (a lizard man). A new difficulty called Nightmare can be unlocked too. When the difficulty is set, any enemy that you destroy will shoot a blue ring projectile in your direction, and the more enemies you kill, the more blue rings will spread all across the screen, which will make it harder to avoid the attacks. To unlock all these new features, simply beat the game in a set difficulty and a new secret will be unlocked. Tsugu-Min is unlocked on Easy, Plissken is unlocked on Normal and Nightmare difficulty is unlocked on Hard.

Nightmare (new difficulty): Beat the game on Hard difficulty.
Plissken (new character): Beat the game on Normal difficulty.
Tsugu-Min (new character): Beat the game on Easy difficulty.

Debug Menu
At the title screen, press +, 1 and 2 at the same time to access the Debug Menu, where you can access what character and weapons you can have, along with a Stage Select. You can also access test levels and a Sound Test and you can toggle whether you get hurt by enemies.

Press "+, 1 & 2" at the Title Screen: Access the Debug Menu