Use the command line utility findup bundled with the fslint official package. Find it in the installation directory
Let's say, you want to 'delete duplicates, not merge with links' a home directory:
/usr/share/fslint/fslint/findup -d /home/chemist
Simply read the manual (?!)
Usage: findup [[[-t [-m|-d]] | [--summary]] [-r] [-f] paths(s) ...]
If no path(s) specified then the current directory is assumed.
When -m is specified any found duplicates will be merged (using hardlinks).
When -d is specified any found duplicates will be deleted (leaving just 1).
When -t is specfied, only report what -m or -d would do.
When --summary is specified change output format to include file sizes.
You can also pipe this summary format to /usr/share/fslint/fslint/fstool/dupwaste
to get a total of the wastage due to duplicates.
For more information, see the FsLint Official Documentation
FsLint homepage: http://www.pixelbeat.org/fslint/