Everything! But if I'm only allowed to pick one thing, it would be trying out the new Pokemon and the new Fairy-type out.
This. Especially the Fairy-type. So far Spritzee is my fairy of choice(picking Y) but I want to see the rest of the new Fairy types for a final decision, especially this Gen's pseudo legend(98% chance it'll be Fairy-type). I will be using only new Poke-fairies though.
Official hot fudge sundae of the IDF Official Hydreigon of the Pokemon B/W 2 Boards.