I'm loving The Witness. It's a beautiful game, and challenges me in a way very different from just about any other puzzle game I can think of. I highly recommend it to anyone looking for a brain teaser and something off the beaten path of modern games.
My brother is currently attending the DigiPen School of Technology working on a degree in video game programming / design. He's an avid gamer but has missed some of (IMO) the best games of all time, specifically, the Half-Life saga. Naturally, I email him recommending these games in the hope of inspiring him or, at the very least, giving him a better understanding of some of the good games he's missed out on and where the industry came from. I even offered to buy the games for him if he didn't want to pay for them himself. Well, he acquired the first Half-Life game and started playing it. This was his response: