Not so much a crazy horse, but her owner that apparently wanted me dead.
Years ago, I took care of this lady's two horses from time to time when she was out of town, etc. One was an older gelding, and the other was a HUGE German Warmblood cross mare. The gelding was no problem, but the mare tried to kill me on various occasions.
The first incident was while hand-walking her. The owner asked for her to be hand-walked x-amount of time on x-amount of days, but left out the very vital information in that I could NOT walk the horse in certain areas of the barn. Not knowing this, I walked her (obviously) wherever I wanted. We were in the open jump field and the horse COMPELTELY flipped out; rearing, bucking, flying side to side and LEAPING in the air, as if I were flying a 2,000+ pound kite! The walk back to her stall was insane and took seemingly forever, PLUS it was getting dark and hard to see (she was a dark horse as well). When I saw her owner again, I mentioned what happened as she calmly replied stating something to the affect of "Oh, no, you can't walk her in the jump field, she will go crazy".
Thank you for telling me now!
The second attempt to kill me was when I was to ride the mare for the owner another time later down the road. She said she wanted her ridden bareback (bareback pad), which I did not find an issue with, as she used to always ride her bareback. Again, the owner went out of town, I rode the horse bareback and while trotting in the (semi-enclosed) arena, she took off bucking HUGE repetitive bucks to no avail. I could not get her to stop and knew I would end up on the ground sooner or later. Deciding to bail, and landing on my feet, I made the right choice as I would have HATED to be trampled by that monster of a horse. Once I was off, she bolted out of the arena. Her owner came back into town, I explained what happened and she just blew it off, stating that she wasn't surprised the horse was fresh, as she had been recovering from an injury and that was the first she had been ridden in a while. But yet... she had me ride her BAREBACK? That makes SO much sense!
Needless to say, I never did anything for her and her horses again that consisted of taking them out of their stalls (still fed and blanketed). Like Waresbear stated, ever since, I have been very selective and cautious when agreeing to ride other people's horses for them. I am more than willing to help out when I can, but a line has to be drawn. I am no longer willing (or stupid enough) to risk MY live with somebody else's horse who is not exercised properly, cooped up and full of spunk, AND (especially) lacking ground manners.