I'm not a gamer (at least not so much anymore, in part because I suck at them), but I'll stick my nose in here to say anything multiplayer that is casually easy to pick up & play, yet challenging/addicting enough to keep interest while also somehow encouraging socializing. I still unwind with simple addictive games like match-three style games, but have absolutely no social life unless I come here to the Fediverse.

It might be a bit daunting at first, but a casual game combined with audio chat (preferably with an optional voice changer for privacy) could be rather appealing to me at times. Maybe with tags on users that indicate subjects of interest so it's easier to find people to talk to (or avoid) about various topics.