Super weapons:
Pause game play and press Up(10), B, Down(2), and repeatedly tap B to fill the weapon meter. Press A for the Claw weapon, and resume game play. Note: This code may be enabled with each new life.

Hidden options:
Hold A + B + C and press Start at the title screen to display a menu with ship speed, difficulty, and sound test options.

Alternate ending:
Press C during the ending sequence. Your character will wave and wink.

Two-player mode:
Use two controllers to share control, with one player flying and the other firing the weapons.

Shoot all weapons:
Continuously tap C while pressing B to fire all weapons at once. Note: This is best accomplished by using a auto-fire controller with C set to rapid fire.