War Thunder - It has so many issues from the grind, to unadressed design issues (IE 10kg HE shells doing no damage on a direct hit), to balance issues including p2w vehicles. That said, under all the shit, theres a solid foundation, and no other game comes close to replicating it.
Super Auto Pets - Its an autobattler streamlined to the point where its the perfect casual game when I don't feel like anything else. It also doesn't have any of the normal f2p traps, and is monitized purely on cosmetics that can also be earned for free.
Edit: I guess Dota 2 counts too. I put a ton of time into that. I'm not a particularly good player, but its one of the best team-based games out there, so I enjoy playing it with friends.