What?! You've never heard of Emacs? The Swiss Army knife of editors? Go check it out right now!
Emacs is essentially a Lisp interpreter with added text editing functionality. Over the years, it has developed into a feature-rich text editor convenient for many applications, especially in the area of software development.
Most Macintosh computers have Emacs preinstalled. From a terminal run the command "emacs" and BAM! You're running Emacs!
Emacs works very nicely with Linux as well. Most, if not all, major distributions offer Emacs as an installable package.
Emacs works with Windows. It's a bit rough, but it's still very nice to have. Fortunately, GNU offers precompiled Windows binaries. Emacs works nicely with Cygwin, too.
Most of Emacs' navigation keys (eg. C-a, C-k, C-y, C-f, and C-b) can be used with similar effect on numerous command lines (eg. bash) and on many operating systems (eg. Mac OS X.)
You don't have to use it, but it's a good tool to have in your arsenal.
