The one thing that comes to mind when I think of pet peeves is the toilet paper going under the roll. Yes, I realize that is ridiculously, insanely small and petty. It is just one of those things that gets under my skin for some reason. My husband does it occasionally. My 6 year old has learned how to change the roll when it needs it and she does it too.
As soon as I see it, I will immediately take it off and flip the roll over so it's going over the top. I feel like I cannot get the toilet paper properly if it isn't going over the top. The annoyance I feel when I see it going under and the relief I feel when I switch it is truly baffling.