I have to shower a particular way, doing everything in the same order. Wet my hair, cleanse my face and rinse. I wash my hair, then condition it, wash my body, shave, wash again then rinse out my conditioner. Annoys me to do it in any other order.
Tea rings left on the kitchen counter drives me insane, I'm single now so no longer have that issue. I'd watch my ex make a cup of tea, I'd be behind him wiping it away. Toothbrushes have to be covered, feel physically sick thinking of any particles attaching themselves to mine or my sons toothbrush. I have to clean my car inside and out once a week, I get really bothered about it if its not done. My main one is I can only use a particular nail varnish brand - if I paint my nails and it's chipped after 1 day, it drives me round the bend.