The hack and slash dungeon crawler Hammerwatch gained a rather juice update earlier this month so I went back to take another look.
When I had previously tried it, honestly, I was a bit let down by the enemy AI. However, the more I played of it the more I came to appreciate it overall. That's especially true after playing a lot of it in local co-op (it also has online play!) and it's turned into a fantastic experience on Linux.
Hammerwatch 1.4 came out earlier this month, which added in a brand new Sorcerer class along with the option of twin-stick controls which actually feels really fantastic. They also tweaked abilities for other characters to improve them, updated characters visuals and so on.
I held off on writing about it due to a gamepad issue in the menus, which was fixed in another patch yesterday so I'm now more than happy to recommend it. It's good if you're alone and it will be a challenge enough to keep you interested, but if you bring a friend or two along for the ride it's even better.
Works great with a Steam Controller as well as a Logitech F310.