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 C-Up + C-Left at the character selection screen to change the boxer's 
outfit and pose. 

Flurry mode:
Spell out RUMBLE, press A + B, and when your opponent is close press C-Down 
+ C-Right.

Fight with Tank Thrasher:
Quickly and repeatedly press C-Up + C-Down + C-Left + C-Right until Tank 
starts to make fun of his opponent. 

Taunts:
Press C-Left + C-Down or C-Up + C-Right during a match to perform a taunt.

Cheap vitamins and other items:
Choose to train your boxer In championship mode. Once in the menu, go to 
aerobics, press Left and immediately press A. If done correctly, you will 
have just purchased a $25,000 vitamin bottle for $500. You can do this 
with any of the training materials by pressing Left or Right then 
immediately pressing A before the screen stops on the desired item. 
However, buying 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 A in-between the two items and you will purchase the vitamins or any 
other item for less money.

Game crash:
When you train a boxer to become a Champ, you will be taken to the 
"Select Boxer" menu to choose another boxer. If you press B, you will be 
taken back to the menu of the Champ boxer. If you choose "Title Fight", 
the game will crash, and you will lose all unsaved data.