Hopefully, this is the right sub for this. I really like forgoing a GUI application for the CLI option whenever possible. They run better, don't have any missing icons, don't require a mouse, fit in smoothly in aesthetics with other work (because it'll be ran in the same terminal, so the theme stays the same), and are just more straight-forward. There are plenty more reasons, but you get the point.
Because sometimes sticking to text is the way to go. I'll give a few examples that many likely know:
-transmission-cli (torrent client)
-dwarf fortress (an in-depth ascii game)
-links (a terminal-based web browser...not the only one, just cool)
For a perhaps lesser-known application:
-macchanger (easily change your mac address, very useful for "trial hour" free wifi)
I'd love to hear of some lesser-known cli applications from the community.
Edit: thanks a lot for all the responses. I'm going to have a lot of fun trying all these out