Fire Shark (Genesis)
This game has debugging material.
Despite the awesome-sounding name, Fire Shark is actually about a biplane saving the world from a powerful, unknown enemy.
Pause the game and press Up, A, Down, B, Left, C, Right, Start to enter a test menu that is simpler than those of other Toaplan Genesis games: the first option selects which weapon you have, the second selects your weapon's power, and the third selects how many bombs you have. Press Start to exit. This works in all versions of the game.