There are plenty of unusual sports that are completely foreign to most Americans, but my personal favorite was sepak takraw, which you can find throughout Southeast Asia.
Sepak takraw is basically a hybrid of volleyball and soccer. Like volleyball, teams take turns striking a ball over a net and into the opponent's side of the court. But instead of using their hands, players are only allowed to do soccer-style moves, such as using their feet, heads, and knees. The only equipment is a net and a ball made of small, woven rattan fiber.
Although you'd be hard pressed to find sepak takraw played in the US, it's been a staple of the Asian Games since 1990.