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.
TreeSize - TreeSize tells you where precious disk space has gone to.
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.