i have been pelted by gravel a few times, unpleasant but not earthshattering.
i do clearly recall one incident. close to 30 years ago, i had a chopped honda. eight over front end and six bend pulls which was a cool name for some hi rise handlebars. anyway i was headin' to work. i was doing about 70 mph. i am still unclear just what happened. either i hit a bird, or it hit me. the impact was dead center of my chest. the collision nearly cleaned me off the top of my bike. if the bird was doing 30 and i was doing 70, that is equal to a 100 mph collision if we hit head on. i never really saw the bird but i knew it was a bird due to to all the the bird guts, blood, beaks, and oh yes feathers, lots of feathers all over me. i do not know what kind of bird it was, but my guess it was an albatross or a bald eagle. it hurt that bad! it knocked the wind out of me and it was all i could do to keep the dirty side down while coming to a stop. i had a technicolor bruise about the size of a bowling ball on my chest. i went on to work and i was subjected to a clear case of insult to add to my injury. my boss and co-worker nearly hurt themselves laughing at me. my boss made me go home to clean up.
I was hit by a BFR (Big Farking Rock) totally out of the blue. I never knew where it came from. All of the sudden, it felt like someone shot me in the shin, nice bruise and the knowledge that you cant massage a sore spot while drive 70 in the carpool lane.
No rocks yet....touch wood...however once a bee hit me in the throat then fell down my jacket and stung me in the stomach! Talk about freaking out with a little bit of pain. One other time outside Toronto got hit by a big grasshopper in the side of the face with visor open.....that was painful. Can't imagine a rock...thank goodness I wear full face.