Some group of college freshmen filled a condom with water and tried to drop it on my head (missed). I snuck up on them and started shit with them. Most were apologetic, but one of the girls gave me attitude and said "it wasn't used or anything." I said "of course it isn't... look at you."
I was pissed at the time, but I've actually felt terrible about it ever since. She wasn't even ugly, but I could tell it made her feel bad. In any case, it was my best work.