999 Creationg Points:
In career mode type in "Best" for your first name and "Buy" for your last name.

Play as "Card Girl":
Beat UFC mode with everyone for "Card Girl".

Play as Bruce Buff:
Get a silver belt w/ a custom character.

Play as Referee:
Get a gold belt w/ custom character.

Play as Ultimate Man:
Get all gold belts with every character. This is the guy on the UFC symbol.

Get a Different Referee:
While a match is loading in Career hold down all four buttons and both triggers.

Ulti-Man:
Win championship-road mode on the hard difficulty setting with any fighter to unlock Ulti-Man's body type, voice, nickname, and the octagon location in career mode.

Unlock Masked Fighter Type and Pro Wrestler Style Discipline:
Win UFC Mode with six UFC fighters

Hints

Survival:
To survive, make sure you do not get too close to your opponent. Keep your distance from him. Don't get in too close. Let him come to you and block his jabs which will leave openings for you.

Don't Hit the Mat:
Before attempting to take the guy down, hit him with some swift punches, and you always want to be aware of when an opening occurs. If you see him trying to get you down, get ready to reverse and get him in the Guilotine w/ a Scissors takedown.

Have 'Em Wear Themselves Out:
If you let your opponent do a series of combos on you, you'll see their stamina go down, hit them right after they have finished hitting you and if you time it right, they could go down with one punch.

Hits For Beating Level 31 Challenge:
Having trouble beating the level 31 challenge (Murray Jr.or Murhpy Jr. I think his name is)? Let him take you to the ground in any round your fighting him in and hit him in the face or body to get his energy down. This has worked 3x already. Enjoy!

GameShark Codes

Infinite Time
C60BE43400000004  

P1 Sudden Death Mode Do NOT Use With Infinite Time 
BF2D3947E0705041
F5A1954F00000001 
 
P2 Sudden Death Mode Do NOT Use With Infinite Time 
C608E434E0705041
F5A1954F00000001 
 
Infinite Stamina P1
197C155B00004348
  
Infinite Health P1
BF2E394700004348
 
Infinite Health P2
F5A1954F00004348
 
Infinite Stamina P2
53BF749E00004348
  
Infinite Skill Points
EF97183E0000270F  

Thanks to Revolution readers The Aj, Arader, Sean, John, Kyle Green, Richard Roodbeen, JohnHunt and Brian Gee!