I often create pages based off of existing ones. While I could create a template, sometimes it is just easier to copy an existing page and change a few lines. It would be awesome if there were an option when looking at the dashboard listing of pages to "duplicate" a page. I suppose it would be nice if it just duplicated it as a draft, since there would probably be now reason to have two identical pages.
This could also be more useful for amateur bloggers who may not be able to create their own templates.