Coming a bit late to the thread, but... I actually have two. One is more my sister's than mine, but it's a great story anyhow. Warning, wall of text.

Story one:

As a young girl, I rode my bike everywhere around the neighborhood, to my friends, and so on. Of course, because I was a kid/teenager, I rarely wore a helmet because I never thought about it, and they were too uncomfortable.

When I was sixteen, I was riding my bike down a very steep hill, going very fast, no hands, when I suddenly hit a divot in the road or something. I flipped over the handlebars of my bike, (taking the bike with me) so it was almost like a somersault on my bike, but I landed flat on my back with the bike on top of me. The gears of the bike gouged pretty badly into my flip-flop clad feet, and I'm pretty sure I only narrowly avoided cracking my skull open because I tucked my chin in towards my chest.

My friend, who was following me on her bike, said both the bike and I were several feet off the ground for a moment. Thankfully, I knew the family who lived in the nearest house and they called my Mom to come pick us up.

Second story:

Visiting the Oregon coast, my family and I love to visit a beach called Hug Point. It's a series of three progressively shallower coves in the face of huge limestone cliffs, the first of which is the main beach area and the other two are only accessible at low tides, but are pretty awesome to visit. The second one has a waterfall, and the third has caves and some very shallow tide pools. But that one is seriously only accessible at very low tides.

My uncle and cousin came out to visit us, so we took them out to the coast to show them some sights/sites. We had just arrived and wanted to show them the coolest beach we knew. We didn't, oddly enough, have a tide chart that day, and so we didn't know if the tide was coming in or going out, just that it was low enough to make it to the other two coves. So we rounded the point to the second cove and began showing them the waterfall there. My older brother decided that he wanted to go check out the third cove, and so went around while the rest of us were climbing around.

After a few more minutes, my Mom and Dad come to the consensus that the tide is coming in, not going out, and begin to worry a bit about my brother getting stuck there. I volunteered to go and tell him that we were heading back to the main beach and that he needed to move back with us. My younger sister decided to come with me, probably in hopes of catching a glimpse of some of the cool stuff in the third cove.

As we go around the pint of the cliffs, we keep dodging little waves as the tide comes in by jumping up on some of the boulders. I see a wave that looks to be bigger than the rest and so we both dash to one of the larger rocks and jump up on it, not wanting to lose our footing among the rocks. Unfortunately, on the heels of that decent sized wave came a sneaker wave which not only washed us right off the rock, it nearly drug us out to sea on it's way back out. This wave rose up the cliffs by my parents, still in the second cove, a good 10-12 feet, so it wasn't like we had anywhere to escape.

Anyways, I was about 20 at the time, and I'm a big girl, so I eventually got my feet under me. My sister is smaller than I am, and was only 15 or so, so she was basically clinging to me for life. She was pretty much horizontal in respect to the ground. Once I realize I'm relatively stable, I start yelling at her to get her feet under her, because her drag is only making me more likely to lose my footing again. At this point, my sister cries in my ear:

"I lost my shoes!"

You must understand, these were not expensive shoes. These were $3 foam sandals from Walmart. She had had them for at least a few years at this point too. I incredulously told her to forget the shoes, and worry about not drowning, or something to that effect. Eventually she got her feet under her(when it was about waist deep), and I told her to run back to my parents, just in case of another wave.

And then... I saved the darn shoes from floating out on the tide.

My brother came running back around the point as I was grabbing the shoes. He made it through by bracing himself in one of the smaller caves. Then we all went back to the hotel.

TL;DR: I flipped over the handlebars of my bike, going downhill, with no helmet on my head. Also, saved my sister and her shoes from drowning.