Rain World is still the best. And it's coming to Vita (and more).
Jonathan Holmes went and chatted with Rain World's developers at PAX. In the background you can see a very early alpha multiplayer sandbox that looks to be in the vein of Samurai Gunn and Towerfall. You get points for eating flies and lizards and killing each other.
Did you know lizard only has one "z"? That's weird.