Mac: When you're typing a word you don't know or remember how to spell, you can quickly get a list of suggestions by pressing the escape key in most OS X text editors. Just type as much of the word as you know, press escape, and OS X will offer up as many possibilities as it knows.
You can look through the list and find what you want, quickly, without the need to use your mouse or bother with multiple keystrokes. Check out the video above for a demonstration.
Mac Keyboard Shortcuts [Dan Rodney]