PAR2 Parity Files are used to repair corrupted files and are very frequently
used on usenet for the posting of binaries.
http://parchive.sourceforge.net/

Shared Mime Info does not provide a mime type foir this, and it has lead me to
great frustrations when trying to click on par2 files from Nautilus.

I added the following to my /usr/share/mime/packages/freedesktop.org.xml and it
seems to work:

  <mime-type type="application/x-par2">
    <comment>PAR2 Parity File</comment>
    <magic priority="50">
      <match offset="0" type="string" value="PAR2" />
    </magic>
    <glob pattern="*.PAR2" />
    <glob pattern="*.par2" />
  </mime-type>