Especially interested in those things that keep coming up at workplaces, at home, or anywhere between.
Maybe the people with these problems have not (yet) been exposed to the solution, or maybe it runs counter to intuition and doesn't 'stick', but our collective knowledge knows. And you know. It might even drive you a little crazy that it keeps coming up.
Some examples: Date formatting ( https://xkcd.com/1179/ ) and data integrity (Reed–Solomon error correction), or even more "mundane" things like how to fairly split something up between two people (one splits, the other chooses).