Another new mode for Kid Icarus - automatic card battles.
Nintendo had three demos for Kid Icarus: Uprising at E3 -- single player, multiplayer, and card battles. The card battles weren't really playable; they were just a demonstration of the AR technology. Nintendo had a collection of "idol" cards featuring heroes and enemies from Kid Icarus, including names, character artwork, and each character's alignment.
Placing one card down worked similarly to the AR cards included with the 3DS system, though they were not cross-compatible. Place two cards facing each other, and the characters would battle each other until one or both were defeated.
The concept certainly has promise, but the demo was presumably early in development, as all you could do was watch the battle. Characters seemed to have set strengths, and it did not matter who you pit against each other. Nintendo has yet to announce how they plan to distribute the cards, though a few were given out at E3.