My new favorite shortcut (if I can remember it)
Let's say you're looking at a webpage in your browser. But you want to be on a different webpage. How do you switch?
Ctrl-L will jump to and highlight the address bar, so you can type a new URL or search query. No need to touch the mouse... just type!
Alt+D and F6 perform the same function, apparently, though not across all browsers. (I searched to find out why there are so many shortcuts to do the same thing, got a little sidetracked, and ended up at this handy Wikipedia chart. Now I'm overwhelmed with shortcut possibilities!)