Instant Concert certainly ranks up there!! What about Light as Air?
But worst for me recently has to be "Keep Smiling Through" and "Barnard Castle" mainly cos i have had to play them to death ;)
Plus being a Bass player, anything quiet is a waste of time, bring on the loud stuff and let it rip!!!!!
we played a couple of weeks ago at local supermarket, around -10 degrees. slides on basses and trombones were constantly sticking. Ended up doing relays into shop to warm them up enough to play another carol then run back in!!!!
Thank god the pub had a nice hot open fire!!!!!! ;)