I can't stand it when people just push into long queues and usually say something. I know people will say 'just leave it', but this is how they keep getting away with it, by relying on nobody saying anything.
I know there are much worse things in life, but when you've been queueing a long time and you're tired and fed up, it's not nice.
This can apply to other things in life too.
I was queueing to board a plane last night after a long delay, a woman in her 20s decided she didn't fancy the long queue and just pushed in near the front. A woman must've seen me looking irritated so she tapped me on the shoulder and said 'Just leave her, she might not be all there'.