Ladies, for you personally, what was it?

i want to know from ladies out there that have hauled off and smacked a guy, what was your reason for doing it? i want to see how well behaved most guys are when dealing with the ladies. i've heard from a couple that i know that some guys will come by and grab their backside. i find that kind of outraegous. or some of you may just get upset with something a guy says. so what were your reasons for doing it?