Input the following as your name in champ mode. 

Password:           Effect:
NEWVIEW             Unlock All Arenas

Bonus's
     Beat  these  challenges  in  career mode to unlock the following.
NOTE: All fighting style unlockables are random.

Unlockable                        How to Unlock
Arena: Madison Square Garden      Win a match here to unlock the arena.
Arena: The Staples Center         Win a match here to unlock the arena.
Boxer: Ko Rey Mo                  Defeat Rey in the light heavy division.
Fighting Style: Hard Straights    Win matches in ESPN Classic Fights mode.
Fighting Style: Hook Master       Win matches in ESPN Classic Fights mode.
Fighting Style: Judge Jab         Win matches in ESPN Classic Fights mode.
Fighting Style: Lethal Uppercuts  Win matches in ESPN Classic Fights mode.
Fighting Style: Philly Shell      Win matches in ESPN Classic Fights mode.
Fighting Style: Sinister Cross    Win matches in ESPN Classic Fights mode.
Fighting Style: Slickster         Win matches in ESPN Classic Fights mode.
Fighting Style: Smooth            Win matches in ESPN Classic Fights mode.
Fighting Style: Textbook          Win matches in ESPN Classic Fights mode.
Fighting Style: Uptight           Win matches in ESPN Classic Fights mode.