It is pvp in its simplest form: There is one arena, not too big, definately not too small. There is a lobby directly connected to the arena (There is a hole or something to fall into the arena.)
The lobby is special, when someone goes there it saves their inventory and it gives them the basic pvp kit: Full iron armour, iron sword, 5 steak, a golden apple, a bow and 32 arrows. The players drop down the hole into the arena and then it is basically pure pvp. When they die they respawn in the lobby with the kit and go and fight again.
This shouldn't be hard to code I hope. And pvp is fun

This could be a good addon to the mini games as I think there are no real pvp games on the server atm.