This is a simple Terminal command to clean up your 'Open With…' menu if it displays duplicate applications.
Note: the 'Open With…' menu is available by right-clicking on a document in the Finder. It displays a list of compatible applications that can open the document.
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user
Relaunch the Finder to see the effect (
Alt-right-click the Finder icon to relaunch, or logout and login again).