I've had two memorable (?) incidents--was caching in Williamsburg, VA, in July a few years ago and ended up with chigger bites all over my legs. It seems that since childhood, I've developed an allergy and ended up with silver-dollar-sized blisters. Spent a very hot summer caching in sandals.
Another time went caching alone to a site with large boulders--an unusual site here in Northern Virginia. I was climbing over one, slipped and conked my noggin on another. Fortunately I did not lose conciousness, but I've not been the same since (at least that's what my SO says!).