I’m wracking my brain: is there a type of coliseum-style combat spectacle in which a bunch of fighters are thrown into an area and are expected to fight each other until only one remains?
The WWF’s old Royal Rumble (which may still be continued by the WWE, I haven’t watched any pro wrestling for the past 20 years) was along these lines.
Battle Royale.
Good cites, thanks!.
Do you know if there are any precedents from the medieval or antiquity periods?
This is what I was going to suggest.
Ultimate Showdown of Ultimate Destiny
Yes there was the melee as part of tournaments for knights which could be conducted as a free-for-all.
The wrestling format was evidently named for a form of gladiatorial combat, battle royal.
As OldGuy says, the medieval melee was similar.
In the SCA, we call that kind of last-man-standing mêlée (as opposed to team mêlées) a Bear Pit. ETA: Well, strictly-speaking, a Bear Pit is where one fighter stays in and others attack him until someone beats him, then they’re in the pit, which I guess is not quite the same thing. Never mind…
On a rather darker note, I recently read an article that Mexican drug lords are sometimes hijacking a bus full of innocent people, separating (and executing) any women & children, then taking the men to an isolated spot and basically making them pair up and beat each other to death with baseball bats. The winners then have to become (low-level) members of the gang.
Sounds crazy, but when it comes to these guys nothing seems to be. I tried to find the article, but Googling anything about Mexican drug gangs instantly turns up the nastiest stuff… :eek:
Things nastier than this? 
2011 San Fernando massacre. It’s a wiki cite, but there are plenty of newspaper reports out there.
In FPS games it’s known as Death Match.