Battlecorps
View map:
Pause game play and press B, A, B, A, Right, A, C, Up, Start. 

Level select:
Pause game play in practice mode. Then, press B, A, B, A, Right, A, C, Up, Start. A white flash will confirm correct code entry. Then, hold Down + A + B + C and press Start. Begin a normal game and press Up or Down at the character selection screen to select a new starting level.