iStat Menus - "An advanced Mac system monitor for your menubar."
Stats - Simple macOS system monitor in your menu bar.
smcFanControl - [Download] smcFanControl 2.
MenuBar Stats - Advanced Mac system monitor right from the menu bar
OSX Activity Monitor - Activity Monitor shows the processes that are running on your Mac, so you can manage them and see how they affect your Mac's activity and performance.
iStatistica Pro - System monitor. Reinvented. 💻 🖥