Bronze class
Select "Championship Mode" from the main menu. Then, choose "New Game" and enter "BRONZE" as a gym name to unlock all class bronze boxers in championship mode. Note: This also unlocks Kemo Claw in arcade mode.

Silver class
Select "Championship Mode" from the main menu. Then, choose "New Game" and enter "SILVER" as a gym name to unlock all class silver boxers in championship mode. Note: This also unlocks Bruce Blade in arcade mode.

Gold class
Select "Championship Mode" from the main menu. Then, choose "New Game" and enter "GOLD" as a gym name to unlock all class gold boxers in championship mode. Note: This also unlocks Nat Daddy in arcade mode.

Champ class
elect "Championship Mode" from the main menu. Then, choose "New Game" and enter "CHAMP" as a gym name to unlock all class champ boxers in championship mode. Note: This also unlocks Damien Black in arcade mode.

Alternate costumes
At the character selection screen, press Circle + Square.

Cheap training equipment
Select the "Train Boxer" option in championship mode. Then, go to "Rumble Aerobics Training", press Left and immediately press X. If done correctly, you will have just purchased the $25,000 vitamin bottle for $500. You can do this with any of the training equipment, however the vitamin bottle will save the most money.

Regain energy
Repeatedly tap [X] + [Square] + [Triangle] + [Circle] after a knockdown. Alternately, rapidly press [X] after knocking out your opponent.