Logitech G602, six buttons on the side. Going clockwise from top-left:
- Cmd+Delete (delete file)
- Ctrl+Right (go right 1 virtual desktop)
- Ctrl+Left (go left 1 virtual desktop)
- App Exposé (show all windows only of the active app)
- Back
- Forward
I find these to be the stuff I need to do a lot a lot. Really handy!