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 ^^')
I’m not sure if it counts as niche, but I like stealth games. Thiefs, Dishonored, Mark of the Ninja.
Discovering secrets unseen, clearing whole levels and running like hell to the next dark corner when I get cocky :D
Have you played Acid Spy ? If not, you can pick it up for ~6$ during sales on steam. Despite being very short it’s well worth it !