TinkerTool - Tinker with the hidden settings of your Mac
CleanMyMac X - Clean, protect and speed up your Mac
Onyx by Titanium - This website provides operating system utilities for macOS
Fossils - Find and clean out all your old unused files
Cocktail - General purpose system modify/repair utility
DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.