Robert Downey Jr - I've got go with his very understated performance in Fur. You don't see his face for most of the movie so it's his voice and his eyes that are conveying everything, and I think it's a wonderful performance of his. I really liked this movie although I know plenty did not.
Chris Evans - I feel like early Chris Evans didn't take a lot of roles that let him flex his acting skills, but that changed with Puncture. This was the first film of his I saw that I felt like he stepped out of his comfort zone. It was very meaty.
Chris Hemsworth - I have to cheat a bit here. Hemsworth does a lot of bigger budget action movies and that's essentially all I've seen from him. That said, I think his best performance is in Rush. People tend to talk about Daniel Bruhl the most in reference to that movie, but Hemsworth was good too.
Scarlett Johansson - Johansson's always had a very mature career. She never had to play a high schooler well into her 20's, she always seemed to grab interesting roles even when she was young. One that I don't think gets talked about enough is more recent, and it's her turn as a romance movie loving woman in Don Jon. I don't think she gets enough credit for how funny she was in this and her accent was absolutely perfect.
Mark Ruffalo - Funny thing about Ruffalo, he was not an actor I liked at all until around 2010. He did the McConaughey thing for me. There just came a point where I started enjoying him and his movies more. One movie he never seems to get enough attention for is Infinitely Polar Bear. Sure, he got a Globe nomination but he should've gotten more. That was such a lovely film.
Jeremy Renner - I haven't seen a lot of Renner's movies to be honest, at least not a lot of his smaller ones. He played that pervert in The Heart is Deceitful Above All Things, which I saw, but a lot of his early work has escaped me. Because of that, I'm going to go with Wind River. Sure, this is recent and popular with Film Twitter but it doesn't appear to be popular anywhere else and it should've been for how important it was.