What are some GNU coreutil extensions that you find you can't live without?

Dunno, since learning Xenix in 1993, I got plenty of work done in UNIX clones.

"[Doesn't] get the job done"? Well, it gets my job done. You are welcome to use whatever you subjectively prefer (I use GNU's date(1) for a few scripts, but would prefer the English date grammar parsing as a tool of its own), but if you are unable to talk about anything in concrete terms there is not point in trying to discuss in good faith and I will just roll my eyes and move on.