SciTE is a SCIntilla based Text Editor.
Author: Neil Hodgson Homepage: http://www.scintilla.org/SciTE.html Family: ScintillaEditorFamily Platform: Windows, Linux with GtK?+ License: GPL
Originally built to demonstrate Scintilla, it has grown to be a generally useful editor with facilities for building and running programs. It is best used for jobs with simple configurations - I use it for building test and demonstration programs as well as SciTE and Scintilla, themselves."
It has a defining characteristic -- it allows/supports TextFolding.
It's highly customizable. Allows for command mapping (KeyBinding)
Additional features can be added through Lua scripts: http://lua-users.org/wiki/SciteScripts
Screenshot: