Multi
Game & Wario: Sketch (Pictionary) game was made for the Gamepad.
Nintendo Land: Zelda's and Luigi's games being the biggest hits.
Super Mario 3D World: Multi 3D Land.
Co-op
Affordable Space Adventures: 3 players max that need to coordinate.
Hyrule Warriors: with a bunch of downgrades to play with someone else.
Never Alone: even though it has some bugs, the game was loved by all I played it with.
Pikmin 3: shame the story didn't have co-op too.