CKEditor - Real-time collaborative future-ready rich text editor
WYMeditor - WYMeditor is a web-based WYSIWYM (What You See Is What You Mean) XHTML editor (not WYSIWYG).
TinyMCE - TinyMCE is a content editor that functions as a plug-in for Wordpress websites.
Editor.js - A block-styled editor with clean JSON output
Trumbowyg - Feature-packed WYSIWYG editor in only 15kB of JavaScript
Setka Editor - Setka Editor enables users to design and create content.