Just read this article about the type of controllers supported with the game.  Your options are:

- Gamecube controller (released by the company and via Wii U GC adapter)
- Switch Pro Controller
- Joy-con (set)
- Joy-con (single using horizontally)

Personally I love the fact that you can use a single Joy-con and that's how I will play.  I don't intend on having more than 2 sets of Joy-cons so I can have up to 4 players, and since Nintendo has always been my party system this is a big deal for me.

So how will you play Smash Bros Ultimate?