Emacs

GNU Emacs is a powerful, extensible, self-documenting text editor.

Installation
Explanation of USE Flags:

Configuration
You can customize Emacs by clicking through the GUI (use ) or with your   which's written in emacs-lisp, Emacs' own Lisp-dialect.

Documentation
For a quick-start documentation, type in Emacs: For further help on how to use Emacs, start  and type Control-h and then r.