CleanMyMac X - Clean, protect and speed up your Mac
Wise Disk Cleaner - Clean junks of Browsers, remove junk and useless files of Windows and Defragment your disk. Wise Disk Cleaner can delete these unnecessary files on your hard disk to free up disk space and make your computer run faster.
Fossils - Find and clean out all your old unused files
SDelete - Securely overwrite your sensitive files and cleanse your free space of previously deleted files using this DoD-compliant secure delete program.
DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.
Avast Cleanup - Next generation tuneup and cleanup for your PC