Pikmin 3
Wonderful 101
Rayman Legends
Wii Party U - Several minigames, such as the Baseball machine and Foosball table.
Nintendoland - Specifically, the Luigi Mansion and Animal Crossing mini-games.
Art Studio (eShop)

Splinter Cell Blacklist

The browser and miiverse.

Not strictly a game, but yeah... its what i use it the most for.

Smash's Spectator mode. I can watch and bet on a match at any time.

Bingo. :(

Arkham City, for me.

-Map available at all times on the pad
-Mark your waypoints
-change eqiopment in real time, instantly
-Scan crime scenes with the pad (and motion controls)
-messages from Alfred come in via game pad
-Pad exclusive code breaking puzzles
-off TV play
-Motion controlled weapons

And this was a launch game!

Pikmin 3 and Nintendo Land... It's kinda sad that one of them is the pack-in game.... :/

You HAVE to go back and play Pikmin 3!!  The reason the game pauses when you touch the map is that it's how you give out orders.

I had three different Pikmin groups doing three different things at once because of this.  You could tap a character and send their group to get fruit and have another character going after stray Pikmin while the third group explores the world.  They explain this but during my first playthrough, I overlooked it.  After a few hours, I figured it out and suddenly, Pikmin was a GotY contender!!

Black Ops 2, local dual screen multiplayer is the best.

ZombiU. Not only uses the functions of the Upad, but also the idea of the Upad. Meaning looking down on it for your inventory or when looting and the looking back up on the screen to see if its safe. It has a few throwaway uses like tapping the screen to set up or tear down obstacles, but uses most of the functions in cool ways.