5. Sam Rockwell
Best known for playing oddballs and eccentrics, Rockwell has actually taken on a variety of roles and might be the most underrated actor working today. Rockwell's breakout role was when he played a crazy prisoner in 1999's The Green Mile. He followed that up with a memorable performance in Galaxy Quest as well as a role in George Clooney's Confessions of a Dangerous Mind. Later in the 2000's, Rockwell branched out a bit more while taking roles in some of the more interesting films to come out in recent years. He turned in an excellent performance in The Assassination of Jesse James by the Coward Robert Ford, but his best role so far came a few years later when he played the lead role in Duncan Jones' sci-fi film Moon. Roger Ebert described Rockwell by saying he "seems to have become the latter-day version of Christopher Walken not all the time, but when you need him, he's your go-to guy for weirdness." While accurate and meant to be a compliment, the quote actually undersells Rockwell's overall abilities as an actor.