In my old wedding band, when drunk people were guaranteed, at least once a night, to come up to the band EVERY GIG and say something about "more cowbell" that they thought was clever and original, I came up with the "cowbell medley" that we would go into in response. We also countered the annoying "Freebird" thing by playing the first verse of Freebird and going into an L.S. medley. Clients really appreciated the way we handled the heckling, and we actually got several referrals because of our antics. Oh, and then there was our mic check song which always got a laugh. Ah, the good old days.
...nah, I hardly ever use cowbell anymore except for musicals. I don't play much Latin jazz around town...