There isn't many MMOs out there that have a PvP mode that involves Dungeons. Got a few on the top of my mind, thought Id share them.
Multi Group Dungeons(2-4 groups) - Every team starts at a different spot, makes their way to boss chamber, kills boss together, Kill each other for the loot, a fatal four way tornado tag match. Then if the group wants to, FFA among the winners. Taken from 2moons
Dungeon Territory Wars - Haven't played PW before, but read up on the TWPvP, seems like a Battlegrounds like thing. Same concept as that but you fight for Underground territory.
Player made dungeons - If creator is online, he can accept himself as being the Boss, or if offline or not in the mood, a AI controlled Boss Mob.
Combat Switches(Heavily depends on how optimized the engine is) - 2 players or 2 groups, fight in a series of rooms against Waves of Mobs. The goal, indirectly eliminate the opposing team, by activating random switches around the rooms which release a new wave of Mobs. Each Room has a time limit, mob respawn and a Mob limit. Once time is elapsed, the next room will open. Once mob limit is reached, you lose, so you have to keep killing. Number of Rooms is set by host from 3-10. Mobs respawn after a certain number of kills, happens in 10 secs.
Room Time, Mobstart/Kill total for predetermined respawn(50% of Mobstart), Moblimit, Switchtypes
Room 1 - 2:00, 10, 75, New Wave(5) - Appears every 30 seconds for 10 secs
Room 2 - 5:00, 15, 60, New Wave(5), New Wave(10) - Random Choice every 25 secs for 15 secs
Room 3 - 7:00, 20, 40, New Wave(5), New Wave(10), New Wave(15) -Random every 20 secs for 10 secs
Room 4-10 same as room 3, but with Friendly Switches(-XX seconds, kill XX mobs, New Wave Protection), and Time Increasers, Respawn rate changers, other weapons.
If both players survive, they enter the final room and must team up to survive a 10:00 onslaught of Mob Waves, you can kill each other, but each amount of dmg you do on the opposing player == 50% of that dmg to you(will not kill you, you'll be stuck at 1 health), NO POTIONs or healing in this room. If you do kill your enemy, if you die you lose and he wins.
What you do in the room determines your reward if you both survive, now heres the fun part you fight each other for your prize.
Winning in Rooms = Predetermined reward.
Surviving Final Room onslaught by yourself = Predetermined reward
Killing other player after onslaught = Activity based reward.
FFA/Team CTF using randomly generated dungeons - A concept everyone knows, but with one change, bases are not on preset areas, and are random like the rest of the map. Flags spawn randomly, not near bases. For FFA CTF multiple turn in points for flag, and is randomly selected after each turnin.
I just thought a dungeon based MMO should have dungeon based PvP