Ubit's post above reminds me of a similar situation. It doesn't qualify as a worst gig ever, because it actually went well for us.. I was playing fiddle with an Irish trad band and we turned up to play a wedding at a smart venue In Wimbledon to find not another ceilidh band but a disco taking up the entire stage. There were piles of speakers, lights, smoke machines and junk all over the place. The DJ was an arrogant fat git - when we asked if he could make some room for us, he sniffed contemptuously and refused. So we set up at the side of the stage and played and everyone enjoyed us. The clincher was that we had a high quality EV PA, so we sounded great. By comparison, our hero's massive pile of gear was the cheapest, nastiest disco equipment possible. It sounded like a portable radio, but staggeringly loud and distorted. As soon as he started playing his stuff, the place emptied. Hardly anyone got up to dance and the organisers could be seen complaining to him. Very satisfying. We just stood at the bar smiling contentedly and watching him suffer.