Leaving the machine overnight
One of my ex students left his R22 parked at a very exclusive hotel overnight in southern England, only to look out of the window to see a group of drunken revellers seeing how many people could swing on the tail boom. Needless to say he then had to stay up the rest of the night to keep watch over it, which rather spoilt the ambience of the intimate night away with the less than impressed new girl friend.