Using 3D printer parts and his own ingenuity, YouTube user Jose Julio has created an air hockey robot. Using a robot vision system with an overhead camera, the robot scans the direction of the puck, anticipates the trajectory and reacts accordingly. It can be set to strategically react only defensively, only offensively, or a combination of both. 

In short, it's pretty awesome. To learn more about how Julio made his robot, he's detailed everything on his blog.