Aurra Sing is a fallen Jedi Padawan who later became a bounty hunter. Also, former Jedi Knight Tahiri Veila became a bounty hunter after the Second Galactic Civil War. Other Force-sensitive bounty hunters include Cade Skywalker, at one point A'Sharad Hett, Gula Dwan, Kir Kanos, and Tol Skaros.
Now this is debatable. In the book Imperial Commando 501st by Karen Traviss there is a jedi that "quit" and became Mandolorian. It's debatable weather he is a bounty hunter though.