top two choices for me are pokemon walking behind you and hidden base (aka secret base)
specially with street pass/spot pass on the 3ds hidden bases could be great. just give some great customization in it, ability to fly strait to it (maybe dig to it as well?) it be great too if you could have your own little "daycare" type thing where you can let two pokemon out (size permitting) that roam around your base.
dandelion + flabebe + fairy wind = saddest moment in pokemon. 3ds fc. jd, 0602-6823-9646 or 0146.9112.0071