This didn't happen to me (thankfully), but a good one none the less.
A couple that I often road bike with was out on a mountain biking trip. The wife had a bike problem and fell in the middle of the trail. The husband, either too close or not paying attention, ran over her. I mean really ran over, her leaving very discernable tire tracks across her jersey. He crashed hard just a few yards away. No immediate severe injuries, but they both went to the hospital where they were given pain killers for the inevitable morning after soreness.