turkey sandwiches!
If the “Open With” context menu lists applications multiple times (I had three each of VLC, MPlayer OS X, and RealPlayer), you can rebuild the LaunchServices database with lsregister:
/System/Library/Frameworks/ApplicationServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain userpreviously: Quicktime vs Vlc Fight!