Well, there's a new Hasbro action figure fan choice, and I'd like to humbly submit a nomination:
Bastila Shan
Why Bastila? Well, let me give you my reasons:
1. A large number of requests for an expanded universe character would open the doors for MORE expanded universe characters: Darth Malak, Exar Kun, Quinlan Vos, the Solo kids, and the list goes on.
2. There are few enough female Jedi figures, so it would add another one out there.
3. Do we really need another version of Dannl Faytoni or Ack-Med Behk? Yakface? Squidface? Neimoidian #3?
4. The Knights of the Old Republic games are, outside the films, my favorite bit of Star Wars. Don't get me wrong, I can't wait for my Dark Horse comic fix every month, and there's no better place for the further adventures of Luke, Han, and Leia than the novels, but where else can you vicariously live your Star Wars adventures in such a satisfying manner?
And if you're not going to vote for Bastila, I understand.
But as a runner-up, may I suggest Darth Revan?
http://www.wizarduniverse.com/magazines/toyfare/TF20051214-tf_poll.cfm