Quickly toggle Track Changes on and off using Ctrl+Shift+E. In 2013, this happens in Simple Markup for less mess.
Tired of pounding backspace to get rid of the word you just typed? Try Ctrl+Backspace. Hit it only once by adding the Ctrl key to delete the last word you typed.
How many times have you wanted to tab inside of a table cell and ended up in the next one by pressing tab? Just use Ctrl+Tab, and now you can tab within a cell.