Jai Alai
Jai Alai (pronounced: high-lie) has become more and more obscure over the past decade. This is largely in part because the sport is insanely dangerous and doesn't tend to fly with American audiences. The other part is that American audiences practically control the sports world and what the rest of the Earth views, so there's that.
The Nature of the Game
Evidently, only deaths that have occurred because of Jai Ali were all instantaneous. When a player is hit square in the head by a ball that's traveling upwards of 200 miles per hour, their brain just stops functioning. This has only happened a handful of times over the past few years, but for some reason, Jai Ali players just won't wear facial protection. Go figure.