Ready 2 Rumble Boxing cheats and cheat codes for Nintendo 64

Choose the "Championship Mode" at the main menu. After, select 
"New Game" and enter the following codes a gym name.

Unlock all boxers in bronze class and Kemo Claw in arcade mode:
Enter "BRONZE" as a gym name

Unlock all boxers in silver class and Bruce Blade in arcade mode:
Enter "SILVER" as a gym name


Unlock all boxers in gold class and Nat Daddy in arcade mode:
Enter "GOLD" as a gym name

Unlock all boxers in champ class and Damien Black in arcade mode:
Enter "CHAMP" as a gym name

Change costumes
Hit C-Up + C-Left at the boxer selection screen.

Taunts
Hit C-Left + C-Down or C-Up + C-Right during a match.

Buy vitamins for $500 instead of $25,000:
Go to "Train Boxer" in championship mode. After, select 
"Rumble Aerobics Training", hit Left and immediately push A. 
You can purchase any of the training equipment by using 
the same process.