I once hit a high top spin lob in doubles which bounced over the opponents head, He ran back to get a hold of it, and crashed into the back fence, and started bleeding in several places.
Not too funny I admit.
Then there was the time when I was playing a singles match against a woman and she returned from the changeover to serve. She had no balls in her hands and no "bulges" down there that I could see. I was about to remind her to fetch the balls (I assumed she had left them near her bag), when she quickly pulled one out and served. I leave it to you to visualize it.