View another user's files in OS X

Is there a way to (temporarily) view another user's file on OS X other than to change the permissions of the file? I'd like the OS to ask for the user name/password. I guess what I'm looking for is something like Window's idea of running Windows Explorer as another user (ideally at file/directory level only). The ssh idea fails because the Finder cannot recognize the permission granted. An absolute requirement is not to move the user's files.