HW:
Antonio Rodrigo Nogueira
Brock Lesnar
Randy Couture
Frank Mir
Andrei Arlovski
Tim Sylvia
LHW:
Forrest Griffin
Chuck Liddell
Wanderlei Silva
Quinton "Rampage" Jackson
Rashad Evans
Ryan Bader
Rich Franklin
Dan Henderson
Renato "Babalu" Sobral
Tito Ortiz
Ken Shamrock
Keith Jardine
MW:
Anderson Silva
Michael Bisping
Amir Sodallah
Rich Franklin
Dan Henderson
Evan Tanner
Chris Leben
Nate Quarry
WW:
Georges St. Pierre
Matt Hughes
Ben Saunders
Royce Gracie
Marcus Davis
Matt Arroyo
Thiago Alves
Diego Sanchez
LW:
B.J. Penn
Roger Huerta
Kenny Florian
Joe Stevenson
Joe Lauzon
Hermes Franca
Gleison Tibau
Efrain Escudero
And, given the most recent contract dispute between Dana White and the guys out of American Kickboxing Academy, we can safely assume that the following fighters will also appear in the game:
WW:
Jon Fitch
Josh Koscheck
Mike Swick
HW:
Cain Velasquez
Unfortunately, Paul Buentello and Josh Thomson were not signed by the UFC during game development, so they won't make the UFC Undisputed fighter roster.
Other fighters of note who are heavily rumored to be in the game:
HW:
CroCop*
Eddie Sanchez
Mark Coleman
LHW:
Mauricio "Shogun" Rua
Thiago Silva
Lyoto Machida
Stephan Bonnar
MW:
Nate Marquardt
Thales Leites
Patrick Cote
WW:
Karo Parisyan
Matt Serra
LW:
Clay Guida
Gray Maynard
* These fighters are no longer contracted with the UFC, but were UFC property while the game was actively being developed. If they signed a contract similar to the AKA contract, then they will be in the game.
One more item of note: Even though a fighter may have been 'scanned' into the game, that doesn't guarantee that they will be included in the game. A marginal fighter could be cut from the final UFC Undisputed fighter list and replaced by an up-and-coming fighter.
If you'd like to preorder the game, Amazon has it here for the Playstation 3: UFC Undisputed
And here for the XBOX:
UFC Undisputed
