dupeGuru - dupeGuru is a tool for finding duplicate files on your computer.
SDelete - Securely overwrite your sensitive files and cleanse your free space of previously deleted files using this DoD-compliant secure delete program.
AllDup - AllDup is a freeware tool for searching and removing file duplicates on your Windows computer.
CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.
Czkawka - Multi functional app to find duplicates, empty folders, similar images etc.
Clean Master - Some users swear by it, some call it a glorified snake oil that does more harm than good. That can be said about any snake oil, but what specific brand of snake oil can boast almost a billion downloads around the world?