I'd love to try polo. My hand-eye coordination is terrible, so I'd probably be awful, but it could be fun. Haha or jousting! That would be interesting!
Racing I guess. I like speed!
I already do some dressage, jumping (only a bit) and trekking but I would love to try eventing! I would discover new sensations and another way to ride outside :)
I tried horse-ball and loved it!