What’s your favorite commandline oneliner?

Did you search for times this has been asked before? I asked once (about bash) and got a lot of good answers.

https://news.ycombinator.com/item?id=18898523

p.s. Being specific is good in questions. It's unclear whether you want just zshell things. I don't know how that differs from other shells. Also, "fav one liners" - you mean aliases/functions/scripts presumably, but that's also unclear.

echo "fortune | cowsay" >> .profile