A community site offers a growing list of Mac OS X tips and tricks that require digging into the Terminal. Some very useful, others just for fun, the tips are ranked and commented.
The Terminal Tips & Tricks list is located at Super User, a collaboratively-maintained Q&A site. Some of the tips use apps and services found in the Mac OS X standard installation, while others may require a program from the Xcode Developer Tools package, which is an optional installation found on the system DVDs that come with the Mac.
The top five tips target the following commands (in order):
pbcopy and pbpaste echo opensnoop say mdfind
Now, I prefer GUI tools over entering strings into the command line, after all, this is the Macintosh, the platform that popularized the graphical user interface. Still, there are times when running a Unix-based Mac OS X, that even Mac users will want to look under the the shell's hood. Even me, on occasion.