The most surprising Unix programs
I have found it useful to survey the existing unix utilities (maybe every several years).  I'm no genius but I find things I will use.  One way of course is simply to review the names in wherever your system stores manual pages, and read (or skim) those where you don't know what they do, trying out some things, or trying to remember at least where to look it up later when ready to use it.  Another is by browsing to https://man.openbsd.org/ , then put a single period (".") in the search field, optionally choose a section (and/or other system, not sure how far the coverage goes), and click the apropos button.