Killing Multiple Items in “Open With” Contextual Menu
If, like me, you grow tired of Mac OS X displaying multiple duplicate items in the "Open With" contextual menu item for files then simply enter the following into the terminal to restore the menu to it's original pristine state.
/System/Library/Frameworks/ApplicationServices.framework/\
Frameworks/LaunchServices.framework/Support/lsregister \
-kill -r -domain local -domain system -domain user
You may need to logout then login or force quite the Finder in order to see the change.