I just came across this great list of command line tools for macOS by Saurabh, and to be honest, I had never heard of quite a few of them.
For example, who knew about textutil that can convert text documents between types like txt, html, docx, etc?
Or also a tool like networkQuality that can measure your internet speed? It even gives you a great readable output like this:
Downlink: capacity 105.573 Mbps, responsiveness 64 RPM - Uplink: capacity 6.886
Downlink: capacity 103.467 Mbps, responsiveness 64 RPM - Uplink: capacity 6.880
Downlink: capacity 100.457 Mbps, responsiveness 64 RPM - Uplink: capacity 6.890
[...]
==== SUMMARY ====
Uplink capacity: 8.511 Mbps
Downlink capacity: 20.053 Mbps
Responsiveness: Low (67 RPM)
Idle Latency: 36.917 milliseconds
If you use the command line at all on your Mac, I recommend at least giving this list a once over.