One of my most used tools with pipes on the Mac is `pbcopy`, which copies whatever you're piping to the clipboard.

Copying your public key somewhere? `cat ~/.ssh/id_rsa.pub | pbcopy`

Pretty-printing some JSON you copied from a log file? `pbpaste | jq . | pbcopy`

It's one of those little tools I use daily and don't think about much, but it's incredibly useful.