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.
Baobab - Distributor of workload automation, financial statement reporting, data access, IT Asset Management and Service Desk software solutions.
MenuBar Stats - Advanced Mac system monitor right from the menu bar
Filelight - Filelight is an application to visualize the disk usage on your computer.