Remove duplicate entries in OSX's "Open With" menu

Launch the Terminal and run the following command

/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain user

the above command rebuilds the Launch Services database, which might take a while.

Once the database is rebuilt, you must relaunch Finder for the changes to reflect, which can be done with

killall Finder

Enjoy a shorter Open With menu!!