Notepad++ is a free source code editor and Notepad replacement that supports several languages.
Sublime Text is a sophisticated text editor for code, html and prose - any kind of text file. You'll love the slick user interface and extraordinary features.
Atom will be discontinued at the end of 2022: https://github.blog/2022-06-08-sunsetting-atom/
Vim ("Vi IMproved") is an advanced text editor that allows syntax highlighting, word completion and has a huge amount of contributed content. It also has a GUI version called GVim.
The Kate project develops two main products: KatePart, the advanced editor component which is used in numerous KDE applications requiring a text editing component, and Kate, a MDI text editor application.
GNU nano is a small and friendly text editor. Besides basic text editing, nano offers many extra features like an interactive search and replace, go to line and column number, auto-indentation, feature toggles, internationalization support, and filename tab completion.
Official text editor of the GNOME desktop environment. Has syntax highlighting and is suitable for programming, with support for several languages. It is extensible with plugins.
GNU Emacs is an extensible, customizable text editor—and more. At its core is an interpreter for Emacs Lisp, a dialect of the Lisp programming language with extensions to support text editing. The features of GNU Emacs include:
Bluefish is a powerful editor targeted towards programmers and webdesigners, with many options to write websites, scripts and programming code. Bluefish supports many programming and markup languages, and it focuses on editing dynamic and interactive websites.