I have had two scary falls. The first was a few years ago, I was riding a like 13 some odd hand Arabian gelding, and he hit a divot in the sand or something in the arena, and tripped. He started to regain his balance, but wasn't totally successful, and he ended up flipping over, threw me, and I apparently bounced a couple of times and slid forward, and ended up pulling myself forward really quickly so that he wouldn't land on me. He did end up landing on my ankle, though fortunately no damage was done. I was really sore, but fortunately we were both okay.
Third time was when I got on my Arabian for the first time, she was doing awesome, and I had someone leading her around the round pen, just to get her used to someone on her back. Well I was just about to stop and get off because she was being so good, and the stupid barn cat had to jump up on the rock right by the round pen, from the backside, so you couldn't see her until she was up on the rock. Well needless to say it scared the crap out of my mare who proceeded to take off, and I decided to ditch the horse before she ran into the fence. She was headed right, so I pushed off to the left, but right as I left her back she decided to switch directions, and jumped to the left, which left me flailing in midair to land on the right side of her, and not get stepped on. I ended up landing with all my weight on the inside bottom of my right kneecap, and the guy helping me with my horse had to come pull me out of the arena, while we let my mare run herself out. I couldn't feel my lower leg for about 5 minutes after "falling" off, and had a huge road rash from my jeans. My knee got really swollen, and I had a hard time walking for about a day and a half. Fortunately no more permanent damage than I already had, but it was still very scary not being able to feel your leg, and not even realizing it till someone asked me to move it. I scared the guy bad, because I guess I jumped up to try and get out of the arena, but as soon as I put the weight on my leg to move, I fell over, and couldn't get up again. Now she's absolutely wonderful, and I haven't had any problems since, but it took a bit to get over it.