Howdy,
Shortcut of today is
Ctrl + W
This shortcut is less popular but nonetheless useful if you handle a lot of documents, browser tabs, files, etc. It Closes the current document, window or tab generally without closing the program that handles the respective file. For example if you press Ctrl + W in your browser it will close the current tab but keep the browser open. Another shortcut that has the same function in many programs is Ctrl + F4.
Drop us a line if you know of other uses for this shortcut.
Related shortcut(s): Alt + F4