Harry Enfield's 'Couple' - 'What are you, deaf as well as saggy?' - I use this often.
Not so much an insult, but a come-back that made me snort - we were in a car park looking for a space, found one and duly pulled into it - got out of the car and a bloke (who we had genuinely not seen before) rushed up to my beloved and snarled 'I WAS WAITING FOR THAT SPACE, YOU'RE A FUCKING w***er' - unusually calm, my chap looked up and replied 'But I'm a w***er WITH A PARKING SPACE'. Perhaps you had to be there, but it was rather amusing.