I was switching through my Dock just now, using Command-Tab. I needed to quit BBEdit, so without thinking about it, I highlighted BBEdit in the Dock (with Command-Tab), I kept the Command key held down and hit 'Q'. The Finder stayed as my front application and BBEdit quit in the background. So, there's a quick way to quit an application, without switching to it first.
[Sudo Editor's Note: The Dock must be visible for this hint to work.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002030820472073