Standardbreds, some of them rack on their own, and some compete in speed racking. And where I am there is many standies that are in jumping and dressage shows, there are even shows where I live made for standies. Even some have more cow sence than any quarter horse I've met. There is a famous standie that won three gold metals for jumping in a row, mind you I can't remember it's name.
Standardbreds exspecial right off the track without any training tend to be easy to handle of the ground, but a handful in the saddle. But once they learn the difference between the saddle and the harness they are great. Not really good beginner horses though, without training.
I own and retrained a 16hh bay roan mare Mooney (everyone swears she is a quarter horse), and looking at a 17hh pure black gelding.