While checking the plane today before heading out, I was looking at the linkages in the ailerons. Unfortunately, I kinda forgot it was a particularly windy day, and didn't hold the aileron up, and it slammed down on my fingers, causing a bit of a cut.
When I teach the walk round I always warn students about this potential hazard which can also be caused by another pilot moving the opposite aileron.
Also if you miss the step getting off the wing of a PA28 you can impale your shin on said step - happened to me and apart from being painful the bruise took a while to heal.