I must be in a very funny mood this afternoon because for some reason this seems like a good idea to me:
How about if you manage to kill another player then you get to write a custom label which appears over their head for a fixed period of time. That is a fixed period of in game wandering around time so no logging off or afk hiding to wait out the timer. Needless to say the labels cannot be turned off by the ganked player.
So after a defeat "Conan the Magnificent" becomes "Conan is a big Sissy" or more probably "Conan is a %$$%% @%%&&"
I think its brilliant.