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.

XML Editor
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
XQuery
Subversion (SVN) Client
XML Editor makes easier the document sharing between content authors by including a Subversion (SVN) client. The SVN client allows you to browse repositories, check for changes, commit changes, update your working copy and examine the revision history.

Other features
Plugin for Eclipse, various editors for DocBook, TEI, XHTML, XSL:FO, SVG, XQuery, WSDL, remote editing, licensing policy, miscellaneous.