When i watched the Minecrack live stream a few days back i saw something that would turn out to be a great pvp map of some sort. They had two factions and allot of players joined them since, well they are the Minecrackers. With over 100 players in their team they built a fort of some sort, if you could call it that. But they built it so fast and so dynamic even tho they could not talk to each other, sort of like DvZ.

I don't know the right people to set something like this up but i have had this in mind for a long time but in my head they had creative for 10 min and there was only 10-20 players in a team. Setting this up with 100 players in 2 teams and let them fight to death and the goal is to make them not able to spawn (Destroying their beds!) if you die while you can not respawn you are out of the game.

The problem here is that i don't know 200 players and if someone is up to the task i think this will be a popular game mode in the Minecraft community.

To summary things up:
2 Teams
~100 players in each team

Goal: Kill all the players on the other team so there is non left.

Teams spawn about 200 - 400 block from each other.

Can be made with more teams but the amount of players in each team is still important.