During the 2nd Edition D&D days of high school and college, we would occasionally get together and play through a Necromancer Maze.
The concept of the Necromancer Maze is rather simple; It is a player vs. player game adjudicated by a game master. The game master is responsible for tracking the position of characters on the map. I believe, in most cases, the players had access to the entire map.
In 2nd Edition, Necromancers couldn't access Illusions and (if memory serves) Enchantments. This meant that Invisibility and other spells that were more painful to adjudicate in PvP were off the table.
How We Played
Each player would submit their necromancer's moves (i.e. I move from here to here) via paper. Then the game master would handle any incidental sighting of other characters. If characters noticed each other, then conflict would ensue.
The game master would pull the players aside and have them resolve their conflict while others were puttering around the maze.
This player vs. player concept was great. We were playing in the age of Mortal Combat and Street Fighter II, and found the spell selection and tactics of the Necromancer's Maze to be very engaging.
Typically, the necromancers were 5th to 7th level, so they had a few hit points and plenty of spells to fire off. The GM would give each player a set of magic items (pick 2): +1 quarterstaff, 1 healing potion, +1 ring of protection, and probably other things of use to those trapped in a dungeon with a bunch of other angry necromancers.
What We Could Do Today
Contrary to what some may believe, I don't play a lot of video games; I tried playing “Zelda: Twilight Princess” when it came out, but lost heart after I spent 15 minutes training and that game was erased. When my brother is in town we'll play Mario Strikers and Mario Tennis. But that is about it.
So the concept of PvP remains somewhat novel to me. I believe this method of play would work reasonably well in today's D&D 4E, but most 4E characters might have too many hit points to make the fights quick enough. I suppose you could have 3rd level characters running around beating each other up.