TinkerTool - Tinker with the hidden settings of your Mac
Autoruns - See what programs are configured to startup automatically when your system boots and you login.
Onyx by Titanium - This website provides operating system utilities for macOS
CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.
Cocktail - General purpose system modify/repair utility
Glary Utilities - The No. 1 Free, Powerful and All-in-one utility for cleaning your PC