The Outer Wilds. IMO, non-violence-based gameplay design is an underexplored space, especially in 3-D games. The Outer Wilds manages to feel like a fully-fledged game, rather than a traditional walking simulator, using exploration as it's core gameplay loop.

Further, it's main progression system is you, the out-of-game player, learning about the world. There's no abilities you gain or keys you have to find. You unlock new areas, not as a programmed game mechanic, but as a function of reasoning about what you've discovered and gaining insight into how the game world works. Any playthrough could be beaten in about 15 minutes -- there's nothing physically blocking you from triggering the end of the game -- but it takes you 15 hours or so of flying around the solar system to accrue the necessary insight to get there.

It's really a special game.