Kiwi application monitor - Kiwi application monitor is a small program which lets you monitor your applications/processes, Windows and User activity.
Stats - Simple macOS system monitor in your menu bar.
Battle Encoder Shirase - Software that controls per-process CPU usage: an “active” software CPU cooler.
iStat Menus - "An advanced Mac system monitor for your menubar."
Processes - https://www.oneperiodic.com/products/processes/
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)