It's not necessarily the best, but I had a very weird insult not too long ago.
I got into an argument with this guy when I was moving into my apartment. He mentioned something along the lines as, "Would you seriously help someone for free carrying all of those heavy boxes?"
I responded as, "Yes I would."
Then he said, "What are you, some sort of Christian? Because I'm not a Christian!"
Yeah I help people out because it's common courtesy, and it has nothing to do with me beliefs. Still was something I won't forget for quite sometime.