It is the most powerful USB cleaning utility ever made.

Features of USBclean 3
Quickly and easily remove pesky junk and ghost files from your external USB drives.
DS_Store, Thumbs.db, .Spotlight, and trashed files take up precious space, and can cause issues on some devices.
Remove them all quickly and easily with USBclean.
Configure USBclean the way you want!
Remove any number of pre-configured filetypes, or add your own custom filetypes for more flexibility.
Remove files by dragging your drive into the handy drop zone, from the system menubar, or by dropping straight onto the dock icon.
You can easily configure USBclean to run only from the system menubar and open at login. It's a snap to auto quit after dropping your drive onto the dock icon.
Clean up those annoying files that don't play on your media devices.
Removal of Mac only files (useful when sharing a USB drive with a friend's PC)
Removal of Windows only files which take up useful space
Removing files of any number of (customizable) filetypes. For instance, to quickly remove all m4a files from an external drive, go to the "File Types" preference-tab and quickly add "m4a" to the extensions field.
Technical Details and System Requirements
64-bit processor
OS X 10.11 or later