Here's something that might suit some of you (it would generally suit my character fairly well).
Heckler: "There's no such thing as magic."
Performer: "Excuse me. What is your name, sir?"
Heckler: "Gerald" (All hecklers are named Gerald, don't ya know
Performer: "Everyone! This is Gerald. Apparently he showed up a little bit late to the party..." *Point to your head so as to say, "slow in the brain"*
It gets a laugh, and is adaptable for every type of venue, since it can be done with any kind of tone. With me, it would be a generally polite tone, but if I want to, I can make it incredibly humiliating.
Furthermore, when he gets up in front of the crowd, only to be laughed at, it lets him know that it is your show, and he will not win.