OSX - The little red close button displays a darker circle inside when your document has unsaved changes.
Chrome (Dev Channel): Displays “Hold ⌘Q to Quit” instead of immediately quitting to make sure you didn’t intent to press ⌘W.
Gedit - When trying to close an unsaved document in Gedit a dialog tells you how much work will be lost based on the time since the document was saved.
OSX - Hitting “Esc” chooses Cancel, hitting “Return” chooses Save, hitting “D” chooses Don’t Save. Allows you to control this menu without using a mouse or trackpad.
/via Andrei Herasimchuk