Windows Key is not used enough on most machines, since is very convenient for keyboard shortcuts. Latest addition is a shortcut to one new message without having to open Outlook first and then navigate through menus or pressing Ctrl+N within Outlook. I just create a shortcut to “outlook /c ipm.note”. This trick is well described in many articles.
I use more than one program to put my Windows Key to use:
WinKey
http://www.pcworld.com/downloads/file/fid,5506-order,1-page,1-c,alldownloads/description.html
This is free tool once made by Copernic does just what is needed – assign shortcuts to keys. This is my configuration:

WinAmp
I use “WinKey + numeric keypad” shortcuts to handle WinAmp. I can play/pause, change volume, change songs, turn on shuffle an much more with this tested configuration:
