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 ^^')
Isometric Theme Park simulators. I’m in love with Parkitect and have fond memories playing Rollercoaster Tycoon 1 as a kid.
OpenRCT is the GOAT of this genre IMHO