This isn't exactly Boxer related, though I have seen some Boxers do Canine Freestyle. However, there was a FANTASTIC duo whom competed on Britain's Got Talent earlier this year. They made it all the way to the Finals. And they were very much in contention to win, though they did not.

Come and watch a Border Collie named Gin and her adoring teenage owner Kate !
http://www.youtube.com/watch?v=GHyHz2XyHvM&feature=related