Okay, so this is very predictable and expected coming from me, but - Summer Glau as Cameron. She owned that role so, so hard when it would be extremely easy to underact (or even overact) as a robot learning to deal with emotion. Everything about her screamed machine without being soulless about it, and she could make the tiniest facial tic speak volumes about what Cameron was feeling, in her not-supposed-to-have-feelings way.

I also feel the urge to say Kristen Bell and Jason Dohring on VMars, but that one I think I have to consider some more.

(I would also make a case for Arielle Kebbel as Lexi on TVD, if she had lasted more than ONE GODDAMN EPISODE, DAMON SALVATORE, but I guess some things we'll just never know. *huffs*)