Ooh, ooh! I want to join in the post count spam too!
As for these ideas, If someone is owning the opposition that much there is no point in helping them become more powerfull. It would be nice if there playermodel changed to... Say, Rambo when they got 100 kills. 200 could be... Eh... Gordon Freeman? As long as it doesn't cause too much lag I think it would be fitting.