During the game on the second controller press and hold the R and L buttons and hit the A to turn on and off the AI firing mode.

While playing one player, insert the second controller and press L + R + B simultaneously.

You need a controller plugged into the second controller port. In one player mode press L+R+Y and a line of ammo and health will appear in front of you. It will be ballistic ammo, energy ammo, missile ammo, and both large and small health.

Insert another controller and press X,R,and L and the same time.

Hold L+R+A+B while loading or starting a new game. When it loads up, each stage's enemies and bosses will act like your not there! Also you can run down your ammo and it will still fire past zero!