Well, apart from some of the all time greats already mentioned I'd just to input a little something.
Zooey Deschanel.
I know I know, a lot of people say she only ever plays one character and I can understand where they're coming from, at a glance, they're right to assume so. Get to know her and you'll see they're nothing alike, much like the comparison between herself and Katy Perry- they look nothing alike. I love the characters Zooey decides to play and I love how she plays them.
The thing about Zooey that pulled me in (apart from the uncontrollable desire to watch her) was her acting style. In many recent years actresses just try to win an oscar by being over-dramatic, trying to steal the show, shouting, crying and screaming. Zooey on the other hand can scream without raising her voice, she can scream with just opening her eyes that little fraction more. It's her subtleties that make her a joy to watch. Her body language, her eye and head movements and how they move with each other, the shape of her mouth when she talks, her half-smiles, her timing. She's never over the top, in fact, she doesn't have to do much at all but the little things she does do she does perfectly. Example. in "The Good Life" there's a shot where Zooey and the other guy (can't remember his name) are walking down the road. The camera has them both in frame, 3/4 length shot so not close in at their faces at all. The guy is talking about how the cinema owner (who he takes care of practically) lost his wife and as soon as he says that you can see Zooey very lightly and subtly biting her bottom lip.. so subtle. Another is the end of "Gigantic" which the film practically ends on, not as subtle as the other example but as the film relies on it you can't blame it.
After watching her films I'm always left wanting more and not a lot of actresses have done that, in fact, I can't name another one. I suppose I have a soft spot for Zooey but she did pull me back into actively watching movies and that in itself proves to me she was made for celuloid (or, well, silicon? in this digital age).