My one is not very exciting and may come over as mean, but I assure you, I am not mean and if you'd been there, you'd have understood!
I was working as a teacher at a museum where a group had come to do a complicated day of activities. The children were Year 2, I remember, and the teachers with them were very laid back. Whenever we lined up to move somewhere or we were taking turns to do a fun activity, there were always the same 3 very pretty, blonde little girls at the front. After half-an-hour I got wise to this and noticed that they were actually pushing in each time. They smiled winningly at me, hoping obviously to come over as the stars of the class.
Once I'd got wise to it I took satisfaction in letting them line up, watching the entitled three shove others out of the way to get to the front and commence their charm offensive on me and then walking to the back of the queue and announcing that end would be going first. Wow - the outrage! Cue for these girls to try to get to the front (the ONLY place for them), which I have to admit, was quite funny. The bullied, quiet, unassuming children with low self-esteem were all at the back and it was nice to give them a go at being first.
No unkind words were spoken - I was really a very nice teacher! There are just ways and means of teaching entitled little madams and sirs an important lesson in life! And there own teachers just seemed oblivious. But I know ho upsetting it is for some shyer small children to see the same confident and pushy kids always getting what they want.