CLIX ('command line interface for OS X') makes it easy to harness the power of Unix. It becomes both a fish to buy and a series of lessons in how to fish and ultimately a handy way to work.
It doesn't try to rip you off - it tries to teach you, so you become more independent and don't need that line thrown at you all the time.
The CLIX package includes a starter command database with over 1000 (yes, you read that right) system commands for investigating your system status, for cleaning out the junk files, for getting at secret settings for the Dock, the Finder, Spotlight, Dashboard, Exposé, and all of your most used applications, and all sorted for easy access, any way you wish. More Info »
You also gain access for the first time to the tens of thousands of unused files in your BSD subsystem, files no one's really told you about.
If it can be done in OS X, it can be done in CLIX - if it can't be done in CLIX, it can't be done.
And most importantly, CLIX is infinitely extensible: you can add to it at any time and in any way you please.