Matthew Fox in Alex Cross
The Lost alum was almost unrecognizable after losing 40 pounds to play a cage-fighting assassin in 2012's Alex Cross. "I played college football [at Columbia]. I thought I knew my way around exercise," he said of his grueling, five-month circuit training regimen for the role. "Either I was wrong, or things have changed drastically. Maybe it's both. This was full-bore. Many times I felt like throwing up."