http://imgur.com/X439ZrD
Here you have it, Barkey, a WoW actionbar addon that i imagined up a couple of years ago.
As you can see from the Image the Shift, Ctrl and ALT keys are color coordinated,
Thats because i was hoping that in the same way that shift+ up arrow will give you bar number 2 simply pressing shift could get you a entierly new bar, so you would only see the abilitys you have bound to shift+
Same with ALT and Ctrl.
So say for example: Normaly you would have Sinister strike on 1, When you press shift Eviscerate would show up instead, Pressing Ctrl Might bring up Gouge and ALT would maybe bring up Your Gouge macro for your focus target.
I don't know if this would even be possible to implement in the game but it's an idea i'v had from some time and i wanted to share it.
Sorry if my english is abit poor, it's still early in the morning.
Thanks for reading!