Recently while trying to fix a printer I used lpr a bunch of times. It's not exactly new to me, but never fails to surprise people when I use it.
lpr submits files for printing to your default printer in OSX.
Print a file:
lpr README.md
Print the current file in your Vim session, with a cool job name:
:! lpr -T 'cool job name' %
Print two copies to a specific printer:
lpr -# 2 -P specific_printer README.md
This is an invaluable command-line trick.