Here's another oddball sport, though not an international one (yet!). This riding school in Brazil had a bit of fun combining motocross and cross-country horseback riding - same course, two different methods of getting around it!
You can see some photos here.
The explanation on the webpage says it was a bit of a joke. That so many parents like to see their kids get involved in horses because it keeps them away from motorcycles, drag racing and other adolescent shenanigans. But in this group of friends who all train at the local riding school, many are also into motocross. They decided to set up a friendly competition, mostly in father-son teams, with one partner on motorcycle, one on horseback - "oats versus gasoline".