I was once pushed up against a wall by the landlord, held by throat and told I was barred. I was told "you know why". I absolutely didn't. Turned out later the issue was that while I was waiting at the bar, one of my friends made a joke about my appearance. I turned halfway around to say "just fuck off will you?". This happened to be the same moment that the barmaid said to me "what can I get you?". Though I was looking away from her, she made the assumption I had just told her to fuck off and went to inform her manager.
Another time, I touched my nose while waiting to get into a club and was refused entry because "we don't want Cokeheads here, mate".
Also had a friend kicked out of a Spoons for politely asking a passing bouncer what time they closed. I believe this was on a night the clocks went back, so he was unsure if they closed at the first or the second 2am.