Ask HN: Which games do you recommend to improve thinking and reasoning?

I think something like DOTA would be up there, if only because of the immense state space that you have the game and the ability to use your superior understanding of those options to come out ahead of your opponents. Raw mechanics are important at the highest levels, but you can get a lot of mileage through "out thinking" your opponents in draft, in itemization, and in general strategic decisions about what to do, where and when.

Of all the games I've played (which admittedly isn't many), the Witness felt the most like an IQ test.

Mahjong. Only playing for a few years but quickly became my favorite board game ever (I play japanese riichi). Randomness and luck involved but also pattern recognition, reading the opponents hand, and of course the multiple strategies involved. There are a lot of rules that seems very complicated in the beginning but it's not hard to pick up as long as you understand the core concept of the game. And there are great video game versions too which makes it easier to learn and play if you don't have anyone to play with irl.

Into the Breach - turn based strategy where you know what the AI plans to do on their next turn. The same studio made FTL, which I also highly recommend.

Seconded. Poker is a generally applicable set of life skills, imo.