I hate it when im out and i hear kids swearing, i have seen some as young as about 7 and i hate it, i have to say something to them. I have 3 kids of my own and i would flip if i hear them swear, it sounds awful when kids do it.
I also hate it when there is a que and the person at the checkout takes ages and ages and seems not to care about the large que they have, it may be down to impatience on my part but it does annoy me.
I also hate it when im driving and i let people out and dont get a thank you or a simple hand wave, it really really winds me up, so a bit like yours 4getmenot with the mothers with the pushchairs.
By the way i always say 'thank you' when people let me past be it in supermarkets or in the car.