More recently, there was a guy who liked everyone to know that he had, in his own words, "an enormous penis." He tried to get me to tell him how big I was. I smiled and said, "I never kiss and tell."
Finally, I allowed him to workout with me after him pestering me. (I didn't have time to be his coach, and I was on a tight schedule.) After the workout (I have a nice home gym) I went upstairs to clean up and redress as usual. I didn't think anything of me being naked in front of him as I was hurrying to along.
His eyes got big, and he mumbled something. I asked "what?" and he said, "I thought I was big. Now I see the difference," pointing at me. I said, "Well, how big are you?" He just said, "Not as big as you." and left it at that.
He wanted to get together again, but I politely turned him down. I figured being polite and saying no was enough of a message to him that I didn't appreciate his arrogance.