Ready 2 Rumble
Make Your Boxer Talk
Every boxer has two different sayings you can do during the match. Press C-left + C-down for one, and C-up + C-right for the other.
Credit Goes To: Mark Bennett via N64cc

 Make Your Boxer Talk
 Change Player's

 Ultra Combo
Change Player's Costume
Press Top-C + Left-C to change the outfit and the pose of the boxer.
Credit Goes To: via N64cc

Ultra Combo
When your rumble is all the way up press: B and A at the same time. Then you will have your rumble activated. To get your ultra combo to work you must press: c-right and c-down at the same time. When you do that your ultra combo will work. (This trick works for everybody.)
Credit Goes To: Brent Pribyl ( via N64cc