TeX. I was able to use it during school for some beautiful type setting and formatting but nobody I work with wants to use anything other than plain text or unfortunately more commonly binary wysiwyg editor formats. It's frustrating and ugly.
What WYSIWYG binary formats have you been using? OpenDocument is zipped XML. OOXML is also zipped XML. RTF is plain text. Everything else is dead. RTF is too, actually.