i have, twice.
first time i was 18, which made me of legal drinking age where i'm from. had a few american friends in town and we hit the clubs, being able to show their real IDs and get in was a thrill for them. ended the evening at a punk/industrial bar with a mosh pit. everyone there was cool except for one really aggressive dude that kept targeting one of my friends. eventually my friend yelled at him to back off, which was the invitation the prick was looking for - they rolled. i jumped between them and separated them, got a fist to the temple in the process, and by the time security showed up my friend was out of the equation and it was just me and the trouble-maker. unfortunately he was a regular and a friend of the bouncers, so i got kicked out. needed a few stitches to close a small gash over my eye. my friends thought it was the coolest night of their lives.
other time was less dramatic. occured a few years ago at a certain club in DC that we all know and love, back in the days were we could still smoke inside - and my friend, on an all-day tear, decided that smoking something other than tobacco was a good idea. security were real polite (but forceful) about it - "we saw you two smoking, you have to leave", and we didn't put up a fight... we were busted for pure stupidity. we tried laughing it off, but in the end were just embarrassed by the whole episode - so teeenagerish.
anyone else?