Emacs

Emacs denominates Article description::a class of powerful, extensible, self-documenting text editors. The original implementation still updated today is GNU Emacs, a derivative is XEmacs, which was forked from GNU Emacs in the early 1990s. The latter is not the X version of Emacs but a complete separate program.

Available software
Apart from the two big contenders, many lightweight implementations exist, many of which are available in Gentoo:

Ebuild repository
The Emacs project runs an ebuild repository for GNU Emacs and XEmacs (see Project:Emacs/Overlay) which contains a number of packages including many VCS builds. To add the repository:

or

Many more emacs-related packages should now be available for installation.