iStat Menus - "An advanced Mac system monitor for your menubar."
MenuBar Stats - Advanced Mac system monitor right from the menu bar
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)
Stats - Simple macOS system monitor in your menu bar.
iPulse - Using its concise and appealing user interface, iPulse graphically displays the inner workings of macOS on you desktop, menu bar or Dock.
Macs Fan Control - Macs Fan Control is an iMac, MacBook Pro, MacBook Air, Mac Mini and Mac Pro fan control that is the solution of two basic issues namely noise problems and overheating problems.