1. Logan Lerman - The Perks of Being a Wallflower (2012)
Basically because I am biased about this movie, but he was the most likable character I've ever watched. Not many actors could have pulled it off like he did.
2. Robert Downey Jr. - Tropic Thunder (2008)
Hear me out. Is this my favorite movie of all time? Not at all. But think about what he did... he played a totally whacked out Australian guy that was posing/made up as a black guy, and made it totally believable. Regardless of what you think of the movie, it was great work by him.
3. Christoph Waltz - Inglorious Basterds (2009)
The fact that I had never seen him before this movie probably helps him. That opening scene, wow. The way he just made me terrified that he was about to kill everyone in the building (which he did kind of), all while acting seemingly friendly. Great stuff.