oXygen is primarily an XML editor but we use it as a standalone subversion client for version control within the company, it is the best svn client for OSX by far.
The content assistant, XML outliner and the model view are all designed to make XML editing faster and easier.
XML Schema Editor
XSL / XSLT Editor
XSL / XSLT Refactoring
XSL / XSLT Debugger
Subversion (SVN) Client
Plugin for Eclipse, various editors for DocBook, TEI, XHTML, XSL:FO, SVG, XQuery, WSDL, remote editing, licensing policy, miscellaneous.