Oh god, where to start...
Anything to do with hauling scares. Loading, driving, stopping, turning, unloading... I have to bubblewrap any horse I move.
Of course being dragged. I see people with their feet shoved all the way in the stirrups and I cringe. People that ride in tennis shoes gives me the same effect. I ride with my tippy tip toes in and if I feel my foot go farther in, I don't care what gait I'm in, I'll pull it all the way out if I have to. It's SUCH an impacted fear.
Going downhill, even slightly, with speed. A fear I'll have to overcome if I plan on doing eventing (which I do). A horse getting injured with me on its back is also a fear.