Battle Mii (lost Wii U tech demo; 2011)
From The Lost Media Wiki
Battle Mii is a tech demo for the Nintendo Wii U shown at E3 2011. In the Metroid-based demo, Two Miis run around a level, shooting each other and other enemies and targets.
In the 2012 Wii U launch title Nintendo Land, there is a minigame called "Metroid Blast" that expanded on this tech demo, only more refined. However, the original tech demo has never resurfaced.