If you're working in AutoCAD 2006 or one more up to date, at the Command line, type the first letter of the command you wish to start. Do not press (ENTER); instead, press the TAB key repeatedly and watch as AutoCAD runs through an alphabetical list of all commands, beginning with the letter you first typed. When the right command appears in the command line, press to start it.
This isn't a very efficient way to invoke a command but it's a great way of finding commands you never knew existed; try it yourself and you will discover that AutoCAD has a lot of commands…
Also, you can press SHIFT+TAB to walk back through the list.
UPDATE: On Nov. 10th, we posted that you could use CHAMFER as a way to trim up lines without having to change your Fillet Radius. We've learned, from an alert reader, that if you fillet your lines while holding down SHIFT then the current default fillet radius value will be ignored. It's a bold, new world.