Giga Wing Codes -

Play as Stranger:
Enter the Gallery section and press B, X, Y, B(2), Y, X, B at the first screen. A sound will confirm correct code entry. Alternately, successfully complete the game under any difficulty setting without using any continues.

Invincibility for player two:
Select two player mode, and have player one select a jet. Then, press Start + A on controller two when selecting a jet for player two.