Tom Hanks in Unexpected Miracles.
It was fantastic. Filming the final scene required several stops and restarts. Every time the director stopped the scene, Tom Hanks closed his eyes and lowered his head. He wouldn't break character no matter how long it took to start filming again, and there were several breaks that lasted 20 minutes or more. The rest of the cast and crew were hanging out or eating snacks, but he didn't move from his spot until they started filming again. Then he raised his head and continued in his role. And that scene took an entire day to film. Pure genius.