WYSIWYG Editor!

I searched open issues but this feature request did not immediately pop out, so forgive me if it already exists.

It would be nice to be able to edit pages using a WYSIWYG editor right in the browser. Kind of like Yahoo! and Hotmail when using Windows + IE to compose mail, but instead of HTML it formats the pages Wiki-style.

(I am partial to cross-platform, but who here isn't!)