As usual, probably everyone else in the world but me has heard of this by now:
Chess Boxing, complete with its own World Chess Boxing Organisation (or "WCBO").
According to the London Chessboxing Club's website:
"Europe's newest combination sport, ChessBoxing, sees opponents square-up in the ring and across the [c]hessboard. To excel at ChessBoxing you have to be good at both boxing and chess. You can win by checkmate, time penalty, on points or by knock-out. The two chess clocks are set to twelve minutes (24 minutes total) allowing for a maximum of six rounds of chess at four minutes per round. The bout is contested across eleven rounds, beginning with a round of chess, followed by a three minute round of boxing and so on."
(Notice that there seems to be some disagreement about whether the sport's name is one word or two.)
There's no shortage of websites devoted to chess boxing/chessboxing, including an e-zine called, "chessboxing.com" ("The thinking man's contact sport"), as well as sites for national branches of the WCBO in Great Britain, Bulgaria and Berlin.
And, of course, there are YouTube channels, including this one from the WCBO.