Is there a keyboard shortcut that will sign me out of Gmail?
Unfortunately, there isn't a shortcut to use in Gmail for signing out.
But you can copy the sign out link
https://mail.google.com/mail/?logout&hl=en and assign a keyboard shortcut to it, or add it to your bookmarks.
Assuming you are using Google Chrome, use ClickLess, a Chrome extension, to assign a shortcut for the link of sign out, which is mentioned above.
Go to the options of this extension and add the shortcut.
Now whenever you need to sign out. Use Ctrl+Alt+S, a small windows will pop out, press now s which is the shortcut key for signing out from Gmail.
A trick better than shortcut key is just to paste this link on the address bar to sign out... ***