Speaking as an audience member, I do not like heavy handed or mean-spirited responses. (Can you tell I absolutely hate Don Rickles-type humor?) It may shut the heckler up but in my experience it makes the audience uncomfortable. I have come away from a concert like that with a lesser opinion of the musician. I think partly it is because most of us recognize that the heckler is either drunk way past his capacity or he is trying to impress someone he is with. Why ruin his night?

My suggestion: Be honest.    If you are honest about the situation, the chances are good that you will come up with some good one liners. Don't use canned patter- unless it is genuinely funny.