The only celebrity I'd actually vote for is Neil deGrasse Tyson. I've met him, read his books, heard his lectures and the guy is a very level headed genius. I'd love to see him run, he has the academic pedigree and speaking ability. Also he would increase the R&D done in this country a billion times what it is now.
Pair him with a serious businesswoman from the South and he would win.
Marillyn Hewson - Forbes is a solid running mate
Sadly he is too smart to run.