Level Skip
Hold L + R on Controller One and press Start on Controller Two.

Final Level Item
Hold L + R on Controller One and press Y on Controller Two.

Full Shields
Hold L + R on Controller One and press A on Controller Two.

Restore Generator
Hold L + R on Controller One and press B on Controller Two.

Weapon Power-Up
Hold L + R on Controller One and press X on Controller Two.

Full Ammo
Hold L + R on Controller One and press C on Controller Two.

Full Map
Hold L + R on Controller One and press Z on Controller Two.