Another good one is Blade where you see the crowd part and he goes to work on killing vampires.
Anyone got any others.
Marlo Stanfield exits a house and sees Bubbles on the hood of his car with a gun to his head. "Do it or don't," he says, "but I got someplace to be."
The best character introduction to one of the most interesting characters on The Wire. This was the first one that came to mind when I saw the thread title.
As far as movies, I love the introduction of Paul Dano's character in Looper, when he's struggling with his broken hoverbike and yelling at the homeless guy.