After we get the deathmatch arena fixed, I vote for implementing a Calydonian Boar Hunt event where every nation sends a unit, but they are all allied against a single extremely powerful monster. The character that lands the killing blow gets its hide or tusks or whatever the reward is.
The "boar" would have to have overloaded stats to prevent one shot kills and whatnot. It would be attacked by up to 20 something thug/SC level units after all. But more fun than any of that is the chance for players to be deliciously evil by casting spells like breath of winter, soul vortex, or globals like wrathful skies, and trying to kill their allies and the boar.
It may not be MP viable but it sure would be fun.