23. Jack, The American (2010)
Played by: George Clooney
In this underappreciated gem, Clooney plays a solemn American contract killer staying in Sweden with his lover. After she finds out his true identity as a hitman, he disposes of her in bloody fashion and goes about his newly-single life in typical Clooney fashion. As opposed to the other glamorous roles from his past, the actor's role here is that of a cold-hearted killer who spends his time working out alone and crafting custom weaponry.
However, we see cracks in his overly-serious veneer. The vulnerability surfaces when he meets Clara, a woman he falls for. The American is more about tone and atmosphere than action, and because of that, Clooney manages to bring something unique to the hitman role.