copykill looks for duplicate files.
It is written in Python.
I believe it works in Windows, but I have no personal interests in trying it out, but information is welcome.
path.py must be in your search path, for example /usr/lib/python2.2/site-packages/ but consult your documentation.
You can also export PYTHONPATH in *nixes.
All feedback is welcome as long as it's pointed to me, email@example.com is a good place to start.
Rispekts go to Hege for coming up with the name and Jason Orendorff for path.py.