Kodi is an open source media center software with an amazing UI. Links to various media sources and plugins like Plex or PS Vue. Kodi supports just about any operating system you can throw at from Windows to Raspberry Pi. An Apple TV-like ability to turn any display into a smart TV.
Titanium Software's OnyX is a free utility that cleans and optimizes most versions of Mac OSX. Additionally, OnyX pulls and displays important information about system parameters.