I've been recently been thinking about Arkane Studio's Prey which is a immersive sim, with a pretty good rogue like dlc, that probably has one of the strongest hooks of any game I've played. If you liked Halflife, System Shock, or Deus Ex it's definitely worth a play.
Are there any titles that might not have been commercially successful that you feel everyone should give a shot?
Aww man, I loved Heat Signature and Gunpoint both. They definitely deserve some more love.
Both games are by Tom Francis. His new game Tactical Breach Wizards is 'coming soon' as well
An another one to add in the defenestration trilogy :D
Maybe I should replay gunpoint sometime
A lot of the games people have mentioned here are either obscure games I've never heard of or newer titles in niche communities. But Gun Point is an obscure game I have actually played, I think they could have picked a better name for it though for a game where most combat isn't firearms based it's slightly misleading and probably deterred some people.
House of the Dying Sun was one of my first oculus rift games and so so good