- CKEditor 4 - The battle-tested WYSIWYG HTML editor, when you need even more features and legacy compatibility.
- CKEditor 5 - A set of ready to use rich text editors created with a powerful framework - A set of ready to use rich text editors created with a powerful framework.
- Alloy Editor - a modern WYSIWYG editor built on top of CKEditor 4, designed to create modern and gorgeous web content
- http://ccideas.com/howto/drupal-7-wysiwyg-tinymce-is-ugly/ - wysiwyg tinymce.inc has hardcoded
- wysihtml5 is an open source rich text editor based on HTML5 technology and the progressive-enhancement approach. It uses a sophisticated security concept and aims to generate fully valid HTML5 markup by preventing unmaintainable tag soups and inline styles. The code is completely library agnostic: No jQuery, Prototype or similar is required.
- https://github.com/guardian/scribe 
- HTML Notepad - a WYSIWYG editor of structured documents: texts that have hierarchical and semantically meaningful (oxymoron, no?) structure: headers, list, plaintext islands, tables and so on. 
- http://markitup.jaysalvat.com/home/ - non-wysiwyg
- http://benweet.github.io/stackedit/ - markdown