I love Vermintide 2, It released early this year, and after a rocky launch is now in a really good state, balance and bug wise.
I have almost 500 hours in game and have been playing at the highest difficulty level for the last 400 hours.
The game has a small but great community, if you want to reach them you should join the SquirrelSquad discord via the Vermintide Reddit page.
This game has some of the best, tightest melee combat I have ever seen.
If you want to play a difficult co-op game with a high skill ceiling I wouldn't pass VT2 up.

Thanks for reading, I'd love to hear what other niche games people love!