I have a couple:
My books. I have them organized by genre and titles, usually 1 genre per shelf, unless its silly shit like my old manga or comics, those have their own system. My technical manuals are a whole issue on their own. My wife and kids used to drive me crazy when they would borrow a book and just stuff it back on the shelf wherever. I got them to at least put them on the chair or desk and I will return them.
We have two cars and two trucks. My wife's car and my go to work truck needs to be out on the driveway first, as I go to work before anyone else, and my son just parks anywhere he damn well pleases, and not in the spot I gave him. My daughter wont park anywhere but in the garage, because popular culture dictates girls get murdered in their driveway by insane serial killers. at night. home alone. I tried telling her that once the fence closes then you could just run in the front door, as the fence closed would buy her precious seconds to get inside. Not that we live in a bad area, or even near anyone who would do her harm, as most of the neighbors are what I like to call "uber security." I.e. retired military.
Another one is french fries. My wife buys the five pound bags, and will eat almost every one, except a small handful left in the bag, and will go buy a new bag even if there is still enough for a last batch. It irritated me to no end, and she knows it, as shes done it since we got married, so once a month I have to clean out the deep freezer to see almost an entirely new bags worth in all the loose almost empty bags.
Snacks are another ocd thing for me, because I was raised that you got a snack between lunch and dinner, and only then, as between breakfast and lunch was usually fruit or nuts. Nope, my kids will and have polished off boxes of little debbie and other snacks, and yet never gain a pound, and me, I even smell something sweet I get a pudge. and finding dorito bags in their room with dirty dishes pisses me off, as I don't want an exterminator having to invade my home.