The editor I require, needs to be easy to use. Even for people with absolutely no HTML knowledge
The projects I have tried are:
StackOverflow uses Markdown syntax and the WMD Editor
Markdown is a very nice way to create valid HTML but its feature list is much shorter than the TinyMCE Editor. It might be quite useful for your users, provided they don't need the extra functionality.
Other options you may want to consider are: