Twice ( well 3 times actually, but once the boss tore up the bill )

Once In Corfu, had a argument over the amount of drinks he had put on the bill, it was a shedload of beers, i know we were 6 blokes on holiday and had a good drink, but they took the pee and we worked out we had had a few less than on the bill, told the guy to do one
later that night ( well after the club closed in the town, the only club, so it was fairly easy to find us ) we were met by 20 locals all tooled up with baseball bats, 3 of us ran of leaving me and the other 2 behind to face the music, needless to say, a mass brawl took place and the police arrived, we spent the night in the cells, needless to say, still didnt pay the bill

another time in gourmet place, the food took so long to come out, it was over 1 hour, we got bored and were about the leave, some of the food came out, some didnt, so we had a snack and left

3rd was in the US, service was terrible, complained to the manager who tore up the bill and said " eat what you like on us ", we did, he even brought over a few cocktails, we returned in a few nights and he remembered us, made such a fuss of us, we were treated like royalty