'24': The Game Full Cast List (Spoilers!)
This is the list of characters that is (as far as I know) confirmed to be in the game.
From the show:
Jack Bauer (Kiefer Sutherland)
Tony Almeida (Carlos Bernard)
Michelle Dessler (Reiko Aylesworth)
Chase Edmunds (James Badge Dale)
Kimberly Bauer (Elisha Cuthbert)
David Palmer (Dennis Haysbert)
Chloe O'Brian (Mary Lynn Rajskub)
Adam Kaufman (Zachary Quinto)
Ryan Chappelle (Paul Schulze)
James "Jim" Prescott (Alan Dale)
Tom Baker (Daniel Dae Kim)
Aaron Pierce (Glenn Morshower) (doesn't speak)
Max (Thomas Kretschmann)
Nina Myers (Sarah Clarke)
Kate Warner (Sarah Wynter)
Mandy (Mia Kirshner) (doesn't speak)
Characters created just for the game:
Sean Walker
Robert Daniels
Del Toro
Peter Madsen (Christian Kane)
List taken from http://en.wikipedia.org/wiki/24:_The_Game#Characters