Another nifty keyboard shortcut is like an instanteous undo. Say you are adjusting the size of an image and while adjusting you see it really is not what you want to do.

At this moment you have 3 choices:
1. Try to resize to the original and then unclick
2. Unclick and use the Undo button or CTRL+Z to undo the resizing
3. Click the ESCape key while still holding your mouse click. Whatever action you started (move object, resize object, crop object, etc.) is ended you are instantly back where you started before the mouse click!

– Troy @ TLC