Skyrim and Minecraft are already coming, so that's great.
Dark Souls is a big one. Any of them. All of them. Great fit for HD rumble with the left-hand/right-hand equip system. Great fit for portable play with the quick sleep mode option, and sometimes online, sometimes not gameplay.
Metroid Prime Trilogy, remastered in HD with remapped controls, HD rumble support, and support for multiple control schemes.
BioShock: The Collection, with support for motion aiming and HD rumble. (This game would be perfect fit for HD rumble, and a perfect AAA third-party port to latch on to the Metroid Prime constituency we all hope will be built on Switch.)
Super Mario 64, remade in HD with remapped controls and a better camera. Keep the movement and physics the same but make the game look like something new.
Super Mario Galaxy 1 & 2 collection, remastered in HD with remapped controls and support for multiple control schemes.
Zelda HD collection, assembling all the pre-BotW 3D Zelda games in a single HD package with a mostly unified control scheme and interface.