Americans may not get too excited about robots playing soccer, so why not robot football? Well, in Japan there are already regular Robot American Football games.
The competitions, very loosely based on American football, feature five robots per team (they can only field four of the five at any one time). The football is placed in the center of the field and the teams line up along their respective goal lines. Then they all rush to the middle of the field and try to drive, kick, push, and manhandle the ball across their opponent's goal line.
The robot designs are very similar in size and shape to sumo robots - about 20 cm and 3 kg. The competition lasts much, much longer (see the video link below), is very unpredictable because of the odd football shape, and is a heck of a lot more fun.
Robot Football Game Video Click on the television image to play the video [Japanese]
Robot American Football Official Web Site [Japanese]