Long time ago I had a Boot Camp partition and VMWare Fusion installed to see what it was all about. Then one time I deleted it by moving VMware Fusion to the Trash. I have reinstalled my machine at least once since then, getting rid of the Boot Camp partition, and restoring from Time Machine backups but one thing never really left the system and that was "Boot Camp partition" applications showing up in my "Open With" menu.
For example if I'd secondary-tap a file that was playable with iTunes it would also show: iTunes –– Boot Camp partition in the menu. This freaked me out a little but never enough, until now. I got sick of it had to get rid of them. Here's how:
1) Open Finder
2) Go to your home folder, into Library and then into "Application Support"
3) Delete the folder "VMware Fusion"
Turns out this "VMware Fusion" folder got backed up by Time Machine and put back when I reinstalled, unnecessarily lingering around. In the VMware Fusion folder there was a folder Applications containing the "Boot Camp partition" apps which OS X merged into its "Open With" menu.