Over Labor Day Weekend 2009, I spent five days building a robot that could play Pong on a real Atari 2600, using an unmodified paddle controller. The robot was constructed using a Lego Mindstorms NXT kit. There was a PC-based component which handled the video input, playfield recognition using OpenCV, and trajectory projection and movement calculation using a custom algorithm. By the end of the time, I had built a robot that could play Pong decently well, although it was far from perfect.
You can read all about the development of this robot and associated program here: http://www.mathpirate.net/log/category/crazy-weekend-project-1-pong-robot/