So I have a few apps installed (and a few instances of Fluid) and this is what my Open With menu used to look like:
A little Googling found me Many Trick's very helpful Open-With Manager and now my Open With menu is much better behaved:
Open-With Manager won't touch signed apps (think Xcode, QuickTime Player, etc) so if you want to remove any of those from your menu then you'll need your favorite text editor and the following hint: Remove excess 'Open with...' contextual menu entries.
I think OS X will ultimately figure out (give it a few minutes) that you've changed the menu but if not you can run the following command from terminal to clear the cache:
`locate lsregister` -kill -r -domain local -domain system -domain user
Open-With Manager seems to have decent defaults for pictures and movies for if your cup of tea is something else entirely the preferences allow a ton of flexibility.
Enjoy your cleaner and lighter Open With.