8. Nathan Fillion
Sheldon has made it clear that the cancellation of Firefly hit him hard. He was so prepared to be watching the show for years that he had Leonard sign in the Roommate Agreement that Friday nights would be dedicated to watching Firefly. I can only imagine his reaction when it was taken off the air. Something akin to a panic attack comes to mind. Since then, Sheldon (as well as the rest of the gang) have mentioned the show frequently, whether it be as an example of how to properly end the show (the movie Serenity) or declaring FOX CEO Rupert Murdoch one of history's greatest traitors for canceling the show. Since there's next to no chance that the show will ever come back on, why not give the guys the next best thing and give them the opportunity to hang out with Malcolm Reynolds himself. Fillion could stop by Stuart's comic book store for a signing or meet-and-greet, and the guys would get the opportunity to hang out with him for the whole day. I'd imagine some awkward social situation occurring (most likely caused by Sheldon), but with Fillion's laid-back attitude, he'd probably find the situation amusing.