Multi functional app to find duplicates, empty folders, similar images etc.
Dupeguru
dupeGuru is a cross-platform (Linux, OS X, Windows) GUI tool to find duplicate files in a system.
Ophumeleleyo
Detwinner is the simplest and the fastest tool for removing duplicate files from your Linux PC.
Kompare
Kompare is a GUI front-end program that enables differences between source files to be viewed and merged. It can be used to compare differences on files or the contents of folders, and it supports a variety of diff formats and provide many options to customize the information level displayed.
Meld
Meld is a visual diff and merge tool targeted at developers.
Shredder
finds space waste and other broken things on your filesystem and offers to remove it.