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 ammunition:
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.