CleanMyMac X - Clean, protect and speed up your Mac

WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.

CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.

WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.

Outbyte - Outbyte is a cmprehenmsive computer repair tool that is built to address a range of various system issues like clean up your drive, optimize performance and enhance privacy or security.

SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.