One, my horse decided he was going to be a race horse for a day. I think he may have been stung/bitten by something (but we never did find out) and he took off full speed around the arena with NO control. After about 10 laps I was trying to get him into a corner to help me stop him and he started slowing as if he was going to stop - then he shot out to the side and I came tumbling off.
Another time (same horse) we were at an outdoor dressage show and it was rainy and muddy. Everyone's horses were refusing to go into the corners, bucking, etc. So we go out there and my horse is being an absolutely ANGEL, we probably would have won the class if not for what happened. I asked him to pickup him right lead canter and instead he bucked, according to spectators I flew like 6 feet in the air and then I landed on my butt in about a foot of mud.
Another time, I was jumping in a lesson and I guess I was really not paying attention. We were coming up to a little vertical and I guess I just expected him to go over it but he veered off to the side and I did a somersault down his leg and landed on my butt again. Right as I hit the dirt, a friend who was in the stands stood up and yelled "NICE DISMOUNT!" Lol.
And one more that I can remember right now - I was schooling a little pony mare over fences and she refused and I did a flip over her head and ended up on the other side of the jump.
Haha, I have more stories somewhere but I can't remember them right now.