Your most recently played title that ya consider an 'underrated gem'

Inquisitor - absurdly hard RPG with great story. Diehard Dungeon - Well... its not underrated, reviews are pretty good, but most of us never heard about that game.

The Last Tinker

I'm not sure if it's underrated, because it's a "very positive" game but I love Hand of Fate. I bought it in early access and it was apparent from the beginning that the devs really wanted feedback. On numerous occasions they made changes based on forum feedback. If you aren't familiar with the game, it's a TCG action rpg. Basically you have a deck of cards but you also have fights in "arkham" games style combat. You have various cards in your deck which is random and you make choices but some cards force you into combat. Basically a rogue-lite because even when you lose you gain new cards based on completed encounters.