Gaiares

Hold A+B+C+Start at the title screen to enter configuration mode. Set the sound test value to 18. Hold A on controller two and exit configuration mode. Enter the following controller actions to activate the following
cheats.

Level select - Press Start at the title screen to display the level selection screen.

Weapon select: Pause game play. Hold Up and press A to select a weapon.

Full weapons power: Pause game play. Hold Up and press B(2). Resume game play and fire the TOZ.
Note: This doesn't work with Quark Missiles (missiles your ship already has). Those still have to be powered up by capturing ships.

Legendary Power Weapon:
Fire the TOZ completely six times, then capture an enemy ship that normally awards a weapon to access the Tektite Blaster (T-Braster).

During gameplay, Pause, then press and hold... Left, A, and C, then press Start, you will be invincible for the duration of the stage you are on. (Note: There is no sound to confirm code entry.)

To gain access to the options menu, press and hold A, B and C at the title screen, and press Start.