What's your favorite short, stand-alone program that is fun or useful?
When I say "stand alone" I mean not just a few lines of script in a complex software ecosystem. Calls to standard libraries are OK.
kubectl context
and get a menu with a list of all the contexts currently stored in my kubeconfig, an indication of which one is selected, and the ability to select a new one by entering a single digit numeric ID.
It's a fairly trivial thing, but it's been disproportionately useful to me.