Can't recommend this game enough, it's a really good example of how steam's early access should work (updated weekly for over a year). The co-op is a little weird still, and the market is saturated with pixely procedurally generated games, but this one is def worth the ten bucks or whatever it is. I've played it for an embarrassing amount of hours over the last year, and still haven't seen everything.
Crypt of the Necrodancer is some of the most fun I've had playing a Roguelike since Dredmore. It's an absolute blast to play, I keep finding myself jumping in for a session when I have 15 minutes to kill.