iStat Menus - "An advanced Mac system monitor for your menubar."
Stats - Simple macOS system monitor in your menu bar.
Irvue - (previously Unsplash Wallpaper) Gorgeous wallpapers on your Mac.
eul - System & Hardware and OS & Utilities
Übersicht - Keep an eye on what is happening on your machine and in the World.
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)