Your Majesty,
I present these games to your Royal Highness in hopes that you may enjoy them and spare my head the block:
Nintendo Land is an amazing party game, great if you can get people together to have fun with.
New Super Mario Bros. U is also a lot of fun, Nintendo always does great with their first party games and this one is no exception. Lots of mayhem when you add in the WiiU's gamepad functionality.
Zombie U wasn't everyone's cup of tea, but I think the slower pacing of it over other zombie games gave it a unique, tense feeling that is a refreshing take on a common theme.
Lastly, if you are a fan of the Monster Hunter series at all, Monster Hunter 3 Ultimate is a must have. Everything great about Tri and Portable 3rd rolled into one gigantic package. Well worth it.
In conclusion, for me I have found the WiiU to be a great party system and great if you can frequently get groups of people together. Nintendo is king of "couch co-op" which is a sadly fading gaming environment.
EDIT: I don't actually have one, my brother-in-law does. They don't buy too many games for it, the only other game I really want to check out is Pikmin 3. Again, first party title but it looks incredible.