My worst gig was playing for a medieval banquet one Christmas in the late 70s/early 1980s. The crowd were the employees of Barclays Bank in Tywford. After they had finished ramming each others' faces into their apple pie and ice cream, they proceeded to set fire to toilet rolls and throw them up and down the tables. The police were called and I moved my account to NatWest.
Then there was the ceilidh for a wedding reception where the guests were all stoned, drunk or both. Ever tried getting people to dance who couldn't even tell which way is up?