Idea for 1 form of PvP in the game:

A Brenner Style PvP arena where there are like 5 flag poles spaced out over a map. Where you have to control an area to raise that flag in your teams name, and have to occupy an area for a certain amount of time before taking over an area, flag raising and lowering controlled by amount of people from each team in area. One Big timer on each team counts down at variant speed based on # of flags owned over other team. First one to have points depleted loses.

I also like the idea of free for all and other team/straggety types of PvP.