Champ class boxers:
Enter championship mode and enter CHAMP as a gym name. Exit championship mode and enter arcade mode to have access to all the boxers including Damien Black.

Gold class boxers:
Enter championship mode and enter GOLD as a gym name. Note: This also unlocks Nat Daddy in arcade mode.

Silver class boxers:
Enter championship mode and enter SILVER as a gym name. Note: This also unlocks Bruce Blade in arcade mode.

Bronze class boxers:
Enter championship mode and enter BRONZE as a gym name. Note: This also unlocks Kemo Claw in arcade mode.

Alternate costumes:
Press Square + Circle at the character selection screen.

Cheap vitamins:
Choose to train your boxer In championship mode. Once in the menu, go to aerobics, press Left and immediately press X. If done correctly, you will have just purchased a $25,000 vitamin bottle for $500. You can do this with any of the training material, the vitamin bottle will save the most money.

Choose to train your boxer In championship mode. Place the pointer on weight lifting training, which costs $5000, and move to the right. Press the X in-between the two items and you will purchase the vitamins or any other item for less money.

Easy money:
Enter championship mode, set up the game, then start to get a money in the hundreds of thousands. Save the game to one to as many slots as you have free. Go to exhibition mode, load the second player data, wager $20,000, and start the fight. You will get $20,000 for knocking the other man out, even though he is defenseless. Keep repeating this to get as much money as needed. Note: At least 2 free blocks, 2 controllers, and $20,000 are required for this trick. When completed, save turn off the system, go to the memory card manager and delete the temporary saves (while keeping your main save), then repeat.

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