Hmmmm.
One of my most embarressing moments would have to be when my mustang bucked me off in the walking section of a flat class at an A-rated show... oops. With my mustang, I show hunter jumpers and jumpers, and occasionally flat classes, although he usually does well in flat classes, too. On this particular day, I had either won or taken second in every jumping class I had entered. Then, when I was walking him into the arena for the equitation class, I tryed to hand my crop to my trainer... except my mustang hates crops (all it takes is for me to twitch the crop and he takes off, but it is handy if he is thinking of refusing) , and when I started handing it to my trainer, and had only one foot in the iron and one hand on the reins, he spooked from the crop and bucked me off. I landed on my feet though...
Edit: Another time... Ok, so my parents had just bought me this little jumpers/hunter jumpers pony. This pony was very stubborn, and was quite a handful for me when I was only... lets see.... maybe 8 or 9. Not to mention that the pony was only 6, and hadn't been trained to jump a whole lot...
Anyway, I went to my first jumping show on him. It was just a little local show, and the first jump was a straw bale. Well, my pony stopped dead in front of it, dumped me, then continued to eat the straw jump!
At another show, I entered this jumpers class with this pony... Well, in the middle of the class, while I was about to canter another line, he just stopped dead and laid down! I hopped off when he laid down, and then he rolled around in the arena, got up, and galloped over to the judges booth, where he shook off and got arena footing all over the judge!!! It turns out that he really had to pee, and so to get me off, he decided to roll, run around, and shake... lol the judge was good-natured and got a good laugh out of that one. :)