If it's possible to code it would be awesome to get a small gold+xp bonus for "revenge" kills. If you manage to kill the guy who killed you on the previous round (obviously only if he is now on the enemy team), bonus! I think it would encourage interaction, competitiveness and nerdrage all around, which can only be good for the game. Could be open to exploitation, though, if two buddies manage to get on opposite teams on purpose, though I don't think the probability of being on one team then the other every 2 rounds is high enough to be a problem. The bonus would be more for flavour anyways, not a huge prize. Maybe the worth of a tick on whatever multiplier you're on?