Mine is vehicle building games like Stormworks or Scrap Mechanic. It’s so much fun to shoot at your friends with your latest nuclear drone while hiding in your bunker with a better defence system than Area 51 !
I’m very curious about your fav niche game genre !
(I’m sorry for my bad English ^^')
“Open world” puzzle games. What I mean by that is that you can go and solve any puzzle you like in the world. Nothing is linear. If a puzzle stumps you or has you frustrated, you can always leave and go try another one. The last good one I played was The Talos Principle and I’m heavily awaiting the sequel which is supposed to come out this year. Other good ones are the Myst series (the first game is sort of linear in some parts, but the rest are pretty open), Quern, The Witness, The Outer Wilds, and a few others I can’t remember right now.
Well-produced open world puzzle games don’t come out super often, probably due to how difficult it is to make a puzzle game and now you have to incorporate open world elements into that. For example there are over 138 puzzles in the Talos Principle, and some of the last dozen will probably take you well over half an hour to figure out at minimum on your first playthrough. Makes it pretty niche.