Someone in front of me kicked up a stick with her rear wheel as we were powering up to get up a short, steep hill. The stick got spun up by front, bladed spoke and lodged parallel to the ground between the inside of my brake caliper and my rim. The wheel, of course, came to a dead stop. I, on the other hand, did not. I was in the air long enough to say "Aw man!" before driving my right shoulder into the road and splitting the very end clavicle. Fortunately, I was able to mostly keep my head up, so the helmet only grazed the road surface.
This happened the first time I led a group ride using this route, which I had designed and scouted and was really excited about. The group had to go on without me as I was hauled off to the hospital in an ambulance.