SpaceMonger - SpaceMonger helps you understand what's occupying your hard drive and more effectively clean it up without worrying about losing anything important in the process.
iStat Menus - "An advanced Mac system monitor for your menubar."
ZetaWatch - Manage ZFS volumes in the menu bar
Stats - Simple macOS system monitor in your menu bar.
Drive Manager - Drive Manager has been written to help you easily identify drives which are of the same type.
MenuBar Stats - Advanced Mac system monitor right from the menu bar