Probably one of the most unique roguelikes around, HyperRogue has such a mind-bending world it's really quite something. See my previous thoughts here.
Taking place in a non-Euclidean world it can be a little confusing and it certainly is a difficult game. I've never managed to get very far from it, but it's so incredibly interesting it's a game I regularly come back to just to explore some more.
Recently, version 11 was officially released adding in three entirely new lands to explore, new geometries and projections, new music and a few more little improvements. There's quite a lot to take in, even though it doesn't sound like a great deal, so I do recommend reading their blog post on it.
For those doing some gaming on the go or you simply don't have a powerful gaming PC, it's a good bit of low-end gaming that will keep you occupied for hours. You will get lost, confused, amused and perhaps a little dazzled but it's well worth a look. I could go on for a long time about just how weird and interesting it is, I've got a lot of hours in it now and I still find the experience hard to fully describe.