ITT: We take a non-extreme sport and change it to make it extreme.

Marathon but you can sabotage your opponents any way you want. Weapons allowed. Basically the Road Rash game but on foot.

Dodgeball with bocce.

Polo but with rodeo horses.

Water polo but the water is slightly acidic so your skin and eyes start to burn after a while and you can only get out (rotating with other team members) once you score.

Any motor sport but without brakes.

Soccer with bowling balls.

Squash but the room is so narrow and you can get hit by the other player's racket.

Basketball but the court is oiled.