I think most of mine are sensory issues:
Whatever I'm wearing, I need to have a cotton layer next to my skin.
I need to carry nail clippers so that I can deal with a hangnail IMMEDIATELY
I can't sleep without socks on, no matter how summery it is
I can only get out of bed on a "round" number divisible by 5 eg not 8.02am but 8.05am. Ideally a quarter, half or whole hour.
As mentioned by someone on a previous thread, I can only do one "thing" a day like I wouldn't do a big shopping trip AND a major social engagement on the same day.
I'm quite obsessed with the idea of great British eccentrics eg someone who only ever wears purple and has a brandy at 12 noon sharp every day, that sort of thing.
What eccentricity do you have?
Do you know of any great eccentricities which I can cultivate? :-D