Jayne is my favorite character from Firefly.  He's a bad ass mercenary, but sends money home to his mother, so he can't be all bad.  Personally I have always felt he plays dumber than he really is.  By the way, you can learn how to make your own Jayne hat if you can knit and have the time.  

I found a gallery of some guy dressed as Jayne at a convention or something.  The best part is he is wearing the Blue Sun t shirt also available on this site (shameless plug alert!).  Although looking at him I don't know if he will encourage or discourage sales.  Jayne, by the way, is tall (6'4") and in good shape.