A lot of stuff annoys me in the professional game but the thing that winds me up the most is laziness at amateur level.
Playing 5/6 aside footy and people not tracking runners because they can't be bothered or because they "aren't defenders"
I'll play footy with anyone, their ability isn't a massive issue if they put the graft in but when they can't be bothered to put any effort in, its hugely frustrating, no matter how good they are (or think they are.)