I nominate the fight scene from the Jet Li movie "The Mask". The actual fight scene isn't anything great until you get to the end. The woman gets handcuffed and instead of giving up, just ups and chops off her hand to escape.
Oh, and I second Jimmy and Timmy's Cripple Fight. Pure hilarity.
Oh, and my favorite might be Bruce Lee and Kareem Abdul-Jabbar in "Enter the Dragon." It's kind of ridiculous that Kareem's weakness is bright light but that movie was so good and that scene was so memorable for me that I'd put it up there.