6. David Duchovny
Maybe it's time for an American to play the Doctor? David Duchovny was interviewed in 2008 at which point he mentioned that he had no interest in taking over from David Tennant but was a fan of Doctor Who. He expressed some interest in the idea of playing a villain in the show. It's now a few years later and ten years since David played Fox Mulder in the X-Files tv show; given his experience in defeating the alien menace it seems to me that it still worth considering him as a possible candidate for the TARDIS key. The one drawback may be that he spends all his time looking for missing relatives but he is used to working with a companion though Dana Scully may have her own views as to who is in charge!