When people at gatherings and parties etc, whom I don't know, ask me how I am doing, I like to reply that "I'm not doing so good, actually. I went to the doctor and he told me I had probably only a couple of weeks to live." I say I asked him what was wrong with me, and that he said "nothing medically; it's just that, after talking to you for the last 10 minutes, I realized that you are a total and utter asshole, and it's only a matter of time before someone shoots you or batters you to death with a baseball bat."
It really is a conversation stopper if you don't want to talk to the nosy cunt who asked in the first place.
