Things that are unsexy but I can actually verify as having been useful more than once:
In wallet, folded up tissue. For sudden attack of sniffles (especially on public transport), small cuts, emergency toilet paper.
In bag I carry every day: small pack of tissues, multitool, tiny torch, ibuprofin, pad and pencil, USB charging cable for phone, plastic spork, wet wipe thing from KFC (why do they always shovel multiples of those things in with my order ?).
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.