Enter "NEWVIEW" as a first name in Create Champ mode to unlock all venues.
Win a match at one of the corresponding venues in Career mode to unlock it:
Madison Square Garden
The Staples Center
Box as Ko Rey Mo
Defeat Ko Rey Mo in the light heavy division in Career mode to unlock him.
Burger King trainer
Win the Burger King event in Career mode. Then at the trainer selection screen, press Down until the Burger King appears as a choice. He gives you Heart when you fight.
Win matches in ESPN Classic Fights mode or Career mode to unlock various new styles, at random:
After setting illegal blow off in Options, buy the "Elbow Shot" illegal head punch. Use it to counterattack during fights.