Can I make a custom keyboard shortcut available to all users? I've created a keyboard shortcut but it only works for my current user, we have 3 users on our Mac (OS X 10.8.3) but if I set up a short cut, I have to then set the same one up for our other 2 users.

Is there a way to make it universal?
Typically when you adjust a Keyboard Shortcut, the file(s) that are actually effected are in ~/Library/Preferences/ . If you take those same files to /Library (Not the User Library) they should be accessible to All Users. 

Examples might be 

com.apple.systempreferences.plist

com.apple.symbolichotkeys.plist