Last night, after having just finished the book, I watched "A Clockwork Orange" for the first time. I could have easily started a thread about the best book-adaptations after this, but I was even more impressed by Malcolm McDowell's performance of Alex DeLarge. I don't think I've ever seen anyone act with their eyes so effectively.
What I'm looking for in this thread are less masterful performances, where an actor or actress simply nailed their role in every conceivable way, like Tom Hanks as Forrest Gump for example, but performances that made the hair on your neck stand up. Where an actor or actress managed to reach deep into your subconscious and evoke crazy emotions.