Cold Case - Vera. You know what you like, and you'll make sure everyone else knows it, too. ;)

Firefly - Mal. You're a take-charge kind of mouse.

Battlestar Galactica - (based solely on seasons 1-3, obviously) Gaeta. You're always there, but nobody quite realises just how significant a part you play in things until you get your moments to stand up and say "by the way, I'm awesome!"

...they're the only three I've seen. :(