Ask HN: What are some command line utilites that have great UX?

I'm currently building a small utility (mainly for personal use), but I've realized I don't really have any great complex terminal interfaces to model off of. I mainly use programs that are required, not fun, so I was curious: what are the command line utilities that you enjoy using? What programs do you get a lot of use out of, but aren't bogged down with weird options or commands?