6. Warren Beatty (Bill, Kill Bill)
Believe it or not, despite Tarantino's fondness for reviving careers, the iconic role of Bill in Kill Bill was not originally intended for Kung Fu star David Carradine (though Tarantino had apparently been thinking of the actor while writing the part). Warren Beatty was locked in for the role, but if we believe Michael Madsen's story, Tarantino met Beatty at a party prior to shooting, and after listening to his thoughts on the film, decided to fire him because he felt that he didn't "get" Kill Bill nor really seem to care about his part. Of course, it all worked out in the end; Carradine had a brief career revival prior to his death in 2009, and while it's pretty difficult to imagine anyone else in that role executing it as well, one can't help but try and imagine how Beatty would have fared.