Neovim is a hyperextensible text editor based on Vim. It seeks to maximize usability and extensibility, simplify maintenance and encourage contributions.
Geany is a powerful, stable and lightweight programmer's text editor that provides tons of useful features without bogging down your workflow. It runs on Linux, Windows and macOS, is translated into over 40 languages, and has built-in support for more than 50 programming languages.
PAWed is a simple, easy to use, source code editor, written for GNOME2 and utilising Scintilla, which is extensible through plugins (e.g. HTML Tidy plugin) and Python scripting.