Method : If you see all of the Pokémon within the Unova Dex, when you go to talk to Professor Juniper, she will notice that you have seen all the Pokémon within the Pokédex and will offer you a Present. This Present is the special Permit item which takes you to the Nature Preserve where loads of rare Pokémon, including a Shiny Haxorus, dwell

Method : If you manage to capture all of the Pokémon within the Unova Pokédex, when you go to show Professor Juniper, she will give you the special Oval Charm. This item increases the likelihood that your Pokémon will have eggs when in the Day Care Centre