Note - It has been reported that these codes may cause the game to crash in the start menu. To avoid this, once you have selected start game on the menu, turn the Action Replay off (Switch down) & turn it back on once in the game itself.

Infinite Shield:
801C0348 07D0

Infinite Normal Shots:
801CF800 0009

Infinite Bouncing Mines (Note 1):
801CE8D0 0003

Infinite Bouncing Shots (Note 1):
801CF620 0009

Infinite Energy:
801C1944 07D0

Note 1 - Both of these only work if you actually find some of the mines / explosive shots.