I found this: One of the most often used 'tricks' in a GTD user's arsenal is maintaining a collection of personalized shortcuts for different situations, times and places. As you become more and more fluent in the art of GTD, your collection of shortcuts will grow, and the number of keyboard hotkey combos to remember will soon eclipse the number of available keys on your keyboard!
The solution is a mouse (I recommend Logitech or Microsoft branded mice) with a healthy collection of buttons. With my latest mouse, I have 23 commands stored for casual day to day use, all available for my right hand, and I hardly have to lift my finger. With custom mouse driver software though, this is only scratching the surface. One of my personal GTD heroes, Merlin Mann, is rumored to make use of over a dozen "mouse shortcut" sets, many of which are designed purely for use in several of his favorite GTD apps.