Mac OSX – clean duplicate entries in ‘open with’ menu

LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local\
-domain system -domain user

All you have to do is copy and paste this into Terminal and run it… (note: it takes a little bit of time for it to run so be patient)

Relaunch Finder (control+option+click on Finder icon in the Dock)…

Ta-da! The duplicate or old items are now gone!