The human skull can withstand twenty, maybe thirty, solid knocks before caving-in completely. Robots, on the other hand, can take a beating all day long without showing any signs of dropping. And because they have metal fists and faces, each hit is like a massive car wreck in and of itself. In honor of this week's release of the robot boxing film, Real Steel, we look back at the robot fights that really set the bar as far as robot-on-robot combat goes. From Transformers the cartoon to Transformers the Michael Bay movie, here are the best robot fights.