My favourite non-standard tool is pv[0]. In it's simplest use case, pv is a replacement for cat that also outputs a progress bar to stderr. You can use it to add a progress bar (or multiple) to just about any pipeline. I love it because I know if the one-liner I wrote is about to finish in a couple minutes or if it will be a while and I should either write something more efficient, or do something else while I'm waiting.

[0] https://linux.die.net/man/1/pv