The most annoying thing is when you point things out, and it keeps happening anyway. There’s no way not to sound like a bit of a dick when telling people this so it’s frustrating to repeat yourself when there’s minimal-effort things people can do to avoid it, that they’ve already been told about!
General mess and tidiness being the main offender. E.g. Why do people put dirty mugs/plates next to the dishwasher, but NOT inside the dishwasher?