I remember flying down the back of a Sringbok scairbus from Joburg to Perth a couple of years back. Two of the Seth Efrikan lads, obviously on their first trip on a big plane could not resist the availability of free unlimited booze. Result = one toilet cubicle sprayed from floor to ceiling with vomit. I really admired the FA who put on something resembling a third world chemical suit and waded in with an arm full of paper towels to try and clean it up.
I think one thing that really irks is when you get a screaming baby for the duration of the flight. Not the parents or poor kids fault. Just one of those things I guess. I usually find a few quick belts of the brothers Jim or Jack sends me off to oblivion for the remainder of the journey though
