Jayne is probably my favorite, since he gets the best lines out of 'em all. Though picking a favorite is a bit like trying to decide which better cheddar is my favorite out of a box. Or whether I like my heart or my lungs better. Ok, that's getting a little too personal, but you get the point.
And because I can't get enough of sharing this picture...this is why Nathon Fillon is just *THAT* cool.
That's him at a convention...
http://www.gamerfellowship.org/images/nathansocal.jpg
...he was playing the part of River.
I love it when sci-fi actors are themselves fans of the sci-fi genre.