This was an accidental find at work today.
About to hit ctrl+alt+delete, I mistakenly pressed an arrow key while ctrl and alt were already pressed . The result freaked me out for a second, as my desktop rotated 90degrees clockwise.
This works for all four arrow keys. I had multiple monitors connected to my laptop and I was able to do this for each display individually. Click on the display you want to rotate and hit ctrl+alt+arrow.
Why I think shortcut to display rotation is cool? Because this makes a huge difference at school or work when you have to go through long lines of code and do not want to keep scrolling up or down on a landscape display.