It's funny how the mind really only needs a couple of small details to turn it into a pattern.
So I'm in the RiteAid 'round the corner from my apartment, looking to caffeinate myself. I walk over to the cooler, and all of a sudden, someone grabs my ass. I spin around, and it's some skanky looking guy, hasn't shaved in a while, shirt completely unbuttoned, cheap sunglasses, gold chain--never seen him before. As is apparently becoming a habit with me, I really have nothing to say. He mumbles some sort of half-apology about how I look just like his son, and I just stare.
Finally, he starts to back away, and I spring into action. In this case, action means grabbing a coke, and speedwalking to the cashier. On the one hand, I felt like I should have had something clever to say. On the other, though, I suppose I can just be thankful that I didn't do or say anything stupid. For future reference, though, if I feel someone's hand on my ass, the only way that's appropriate is if I know who it is before I turn around. In fact, that may qualify as one of my fundamental rules of the universe, somewhere in the neighborhood of Kant's categorical imperative.