What's your favorite CLI and what makes it great?

As an example one of my favorite CLI’s is the gcloud CLI. Some things that make it great are that their are things like the “—no-launch-browser” flag for if you are running in a headless environment. Another thing I like is that all commands allow you to pass a “—format=json” flag to get the respond of the command as JSON.

I’m curious what CLI’s does HN love and why are they great to use?