"From the start of my career, I've been naked," says Fassbender, whose newest film, Haywire, opens January 20. "I must admit—I initially thought it might be fun. You hear 'sex,' and you think...sex! But this was definitely the hardest job I've done," he says of starring in Steve McQueen's Shame. "I can usually shake a character off, but I couldn't shake Brandon. He had no sensual enjoyment in his life, and since we filmed the movie so quickly, I found myself living in his skin. Keeping him close to me was exhausting, cold, horrible."