It's hard to pick favorites, it really is.
I've been playing Sm4sh since it released a couple of years ago, so that's gotta be one of them.
Animal Crossing new Leaf is pretty great, too. That game helped me through some pretty dark times, and for that it's become a real soft spot for me.
Oh, and Panel de Pon/Puzzle League/Puzzle Challenge/Whatever. It goes by a bajillion names, and has a million faces, but it's such a fun puzzle game! It's super fast and addictive and I love it a ton