Oh, oh... I gots a few!!!
There was this one time I was riding our old (now retired and rehomed) Arabian gelding Mo bareback with a blue (thick braided) shipping halter and attached lead. I'd ridden him bareback a lot, and normally he was fairly responsive... he'd stop, it just took a bit... but anyway, we were galloping (and back then, he was the fastest horse out here where I live)... so, we were galloping on a trail and just having fun... I was really pushing him... the whole shenanigans... hands, feet, voice... all nine yards and then some. He was giving his all for me and we were both having fun. The trail we were riding on forked at a really sharp angle where it turned to head out to the road... anyway, we were coming to it and I started cueing Mo to stop... he completely ignored me and kept going full blast. He absolutely wouldn't stop... I bailed when we hit the turn and the second my weight left his back, he locked his legs and slid to a stop. I wasn't hurt at all and hopped right back on and continued riding for another few hours.
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Then my friend was once riding our old and now semi-retired mare Buttercup. I was on Mo again, and Buttercup was very, very herd-sour... My friend asked me to take Mo down the trail a ile or two so she could get Butters to run up to us, and I did... the second we got a little ways away, Buttercup went nuts and started rearing and bucking and then took off at a run so she wouldn't 'get left'. She bucked, and my friend, wh couldn't reach the stirrups, was thrown. Butters kicked out and her hoof glanced off my friends head... thankfully, my friend wasn't hurt at all, just a little annoyed.
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Got another one with Buttercup... my then eight year old cousin was riding Butters and we all started to trot... Buttercup bucked, and my cousin, who was bareback, flew off her back and did a backflip in mid-air. When she hit the ground, though, my cousin bounced back up and chased after Buttercup screaming 'you stupid horse' and crying.
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Now, just a few years ago I was riding my mare Gypsie with my best friend on my uncles mare Buttercup. We were cantering, and my girl had/has a bucking problem, but I can normally keep her from bucking. Well, we were cantering, and my mare decided to buck. It completely caught me by surprise and I came halfway out of the saddle, and would have just dropped down, but my foot slipped through the stirrup and I was 'stuck' hanging onto my girls neck and hoping that I didn't fall. She bucked a second time and I lost my grip on her neck and fell. She drug me I'm not sure how far, not too far... just a few yards, but trampled me and literally gave me hoof-print shaped bruises... it knocked me unconsious and my mare took off... My friend on Buttercup took off after my mare and when I regained consiousness, my friend was gone, my horse was gone, and I was laying on the side of the road. After a few minutes, my friend came back with my mare in tow, but it took a little while for me to quit shaking. Thankfully, I was fine and so was my mare.
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There was also the time that my mare got ear-mites really badly for the first time. I had her tied and was trying to put medicine in her ears and she freaked and jerked back, broke her lead, and went over backwards... I freaked out because she didn't get up for a few minutes, but she was fine.
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I was trying to bridle my mare once, about two years ago. I'm still not sure what set her off, but she freaked out and jerked backwards... The bridle reins wrapped around my leg and I literally flew through the air and out of the barn she freaked so badly... I landed on a fallen telephone pole and a truck tire and my mare reared up. I saw her hooves in the air, as I was up under her, and she came down barely six inches away from hitting me, and possibly killing me, and then took off. Needless to say, I did NOT ride that day... I was shaken up so badly I just went inside and cried for about an hour