Ugh, I hate the term 'Cheat Sheet'. These are consistent, programmed shortcut keys to improve productivity, not 'hacks' or hidden features.
Anyway, enough of that. To add a few ...
CMD+Q to quit an app - usefully next to Cmd+Tab, so you can quickly navigate and close open apps.
Ctrl and Arrow Key - essentially does the trackpad gestures. Horizontal arrows swipe between multiple desktops, up arrow will open Mission Control.
CMD+spacebar will open Spotlight.
CMD+W to close a window
CMD+T to open a new tab
CMD+N to open a new window