Possibly the coolest application I've seen of the Wii U's tablet controller yet came in a demonstration of ZombiU's multiplayer at a different event, behind a curtain at Nintendo's Gaming Lounge during Comic-Con. It's the first real application I've seen of the Wii U's varied controller types being used for asymmetrical multiplayer gameplay.
Essentially, one player uses the new "classic" controller—which is similar to a modern Xbox 360 controller—to play in a first-person shooter fashion similar to the single-player missions. But the other player uses the tablet to spawn and direct hordes of zombies with the controller's screen showing a view of the entire map.
The player with the tablet is essentially playing a real-time strategy game, deploying forces (zombies) to capture flags, while the player with the classic controller battles the zombies from a first-person view while also trying to capture flags.
There are plenty of interesting and new elements to this mode—for example, the person with the tablet can see the whole battlefield, and can look up at the TV to see what their opponent is doing. The person playing on the TV, however, is limited to what they can see from their first-person vantage. That alone proves to me that the Wii U is capable of some incredible new types of gameplay.