I have two quarter horses that came off ranches.
Salty has the looks and movement to be a beautiful English horse... very light, collected, beautiful carriage, beautiful lateral movements... but he LOVES sorting and is much happier on a trail than in an arena. Well, then there's the brief interludes when he practices for his dream job of PRCA saddle broncing, but they're not hiring part timers right now.
Cedar absolutely LOVES running barrels and it's obvious someone spent a lot of time patterning him on barrels. He also loves running his horse buddies down the fence and turning them back hard. Alas, despite his preferences, enthusiasm and elevated self esteem, he is mine because he's just not... ehrm.... fast. He would probably be a good cart horse with his stout build, though.
At high levels, there are definite types and temperaments that excel in specific disciplines. At low levels, any horse can do any discipline with training and practice. Salty and I are going to try Cowboy dressage, and Cedar and I are going to clean up in the Adult Novice gymkhanas this year.
When my trainer asked me what I was looking for when we were starting our horse search, I told her, "good sports who will happily try a little of everything." I'm lucky to have found them.