This is a community wiki answer. You can edit me with your improvements. Alphabetically sorted.
Inline
Inline editors differ from normal editors as they can edit the content directly, i.e. not placing it inside another element, or inside an iframe.
Aloha Editor inactive since May 2016- CKEditor - starting from CKEditor 4 Beta
- Etch
FresherEditor inactive since November 2012- Hallo
HTML5 Edit inactive since July 2011Mercury inactive since December 2013- NicEdit
- Quill - starting from v0.19
- RedactorJS
- TinyMCE when used with Inline mode
- wysiwyg.js
- medium.js (library independent)
- ContentTools (Library independent)
- Froala WYSIWYG (jQuery)
- Trix
- Trumbowyg (jQuery)
- editable.js
- wysihtml
Iframes
Iframe editors often load the editor or content to edit into an iframe, to avoid styling conflicts.
- bootstrap-wysihtml5
- CKEditor
Mercury inactive since December 2013- TinyMCE
WYSIHTML5 inactive since December 2014
