POSIX Shell
The language that is already installed.
Shell script earns its place in my tool bag—1979, United States—for the most boring reason available: it is on every machine I will ever log into, and it has not meaningfully changed in my lifetime. A script I wrote a decade ago still runs.
I write POSIX sh rather than bash where I can, because “already installed” stops being true the moment you need one particular shell.
It’s what the small jobs are made of. Napkin’s deploy script is one: it runs the tests, the size limits, the browser matrix, and the performance budget, and refuses to ship if any of them complain. There’s no CI service behind it, so the script is the gate. Owl’s browser build is another, and the script that manages the client-certificate authority for my network is a third.