Mine was in 1975 riding a Honda 360 on a trip from Norfolk, VA to SC. It was a comedy of errors actually, since I was also a comedy on a bike too....oh yes, I thought that I was so cool in those days.
I was riding with a Coke in the old glass bottle tucked between my legs at around 55 on a brand new Honda on US 52 in VA. As I raised the bottle to take a drink, I jammed it into my face shield (DOH!) which I had forgotten was there. That caused me to drop the bottle which bounced off of the tank causing a dent. That also caused me to be covered in wind blown Coca Cola which caused me to become rather "peod" and I quickly decided to pull off the road.
Since none of this was very calculated, I pulled off as soon as possible without slowing much into the gravel on the side of the road where I quickly lost control. After this I don't remember much of the next few seconds, because I slid across an intersecting road, collided with a stop sign and dismounted the bike quickly. This was followed with the bike flipping 3 times and myself laying in a ditch (according to a following driver).
When all was said and done, with the bike being loaded up, I noticed a pain in my thigh, a hole in my jeans, and a small amount of blood....and off to the hospital I went. Generally, I was in pretty good physical shape in those days and I sustained mostly bruises with one exception....
At the hospital I watched the doctor extract a thumb size piece of Coke bottle from the top of my thigh.