Blizzard Entertainment's upcoming v1.0.7 patch for Diablo 3 will add PvP duels to the game -- not Team Deathmatch though -- and a new post on Battle.net describes how it will all work. All duels must be initiated by conversing with Nek the Brawler at the inn in New Tristram. After speaking to him, all players in the party will be transported to the Scorched Chapel, a new zone created specifically for duels.
The Scorched Chapel breaks up into four different spaces: the church itself, a graveyard, a nearby river, and a lake. Duels will support up to four players in free-for-all combat, meaning it's every adventurer for him or herself during these fights. There's no scoring and no rewards structure for these duels; as Blizzard explains, the intent "is to provide players a safe, opt-in location where they can fight one another for bragging rights (or maybe science) without the potential for griefing as it existed in Diablo II."
Anything that diminishes the amount of griefing that occurs in the world of video games is a noble endeavor. Unfortunately, there's no word in the post on when v1.0.7 will go live.