If you frequently use the Duplicate tab function in your browser and also love using your keyboard shortcuts, you might be interested to know that there's an easy way to do this in Google Chrome.
Normally, you can simply right-click on the tab and use the Duplicate item on the menu to make a copy of the tab, but there's no easy way to do this from the keyboard (that we know of). What you can do instead is use a shortcut key combination to highlight the location bar, and then create a new tab from that URL.
Just use the Alt+D shortcut key to put the focus into the address bar, and then use Alt+Enter to open that URL in a new tab. The trick is that you don't have to move your thumb off the Alt key—just push down Alt, then hit D and Enter in quick succession to duplicate the current tab in a new tab. Readers will note that this method also works in Firefox, and duplicates the tab without duplicating the tab history — probably saving some memory usage while you are at it.