I have had the worst luck with buttons lately! I’ve lost the buttons off two shirts, and one button off my pants. Fortunately, I carry safety pins.
Things you should never be without:
Spare tire in your car
Money for a phone call–do pay phones exist anymore?
Lady bandaids, if you are a lady
An emergency contact list, kept in the same slot as your drivers license. In case of emergency, this makes it easy for EMTs or police to contact your people.
Things I am never without:
See above, plus, sunglasses and good lipstick.