Unlock everything:
At the main menu, hold Left Trigger then press 
Right, Right, Left, Left, Down, Up, X. 

Bonus characters and costumes:
Beat arcade mode using the following characters to unlock 
bonus characters and costumes:

Character To Use:      Unlock Bonus Characters: 
Gambit                 Bishop 
Bishop                 Blob 
Phoenix Dark           Phoenix 
Betsy                  Psylocke 
Any Mutant Third       Costumes 


Submitted by SpizZers