Not all these injuries as from Cessnas. I have a very derring-do scar under what remains of my hairline caused by gouging out a line of scalp on the sharp back edge of a Warrior pitot blade. The occasion was mid pre-flight, demonstrating upon request to my instructor that I knew where the static vent was, then trying to move forward out from under the wing.
It bled buckets for hours!! I should probably have had it stitched up but was out at Old Buck miles from anywhere, and opted for several pints of tea and a full-fat fry-up over the next few hours while clamping various bits of first aid kit to my head with my spare hand. Didn't go flying that day :-)