Attach a node to a menu link OR attach custom fields to menu links?
Look into like Menu Views or GigaMenu or MegaMenu ... there are a few solutions that let you place a view in a menu.

Then you can either add a field to a content type such as, "include in featured menu" of type boolean, that you use as a Filter in your View. Or, re-use the "promote to frontpage" re-labeled to fit your needs on a specific content type.