Mahjong
I've gotten into playing Mahjong since I had some friends over who were into it. Both my partner and I have gotten hooked and we've both been playing online for a while now.
We mostly play online on Riichi City, but sometimes play on Mahjong Soul if a friend prefers that client. I've also picked up my own AMOS Masters set to play at home or if other people are over since I cant always rely on somebody to bring their set with them.
We primarily play standard Riichi Mahjong rules, but if we've got a beginner with us we'll usually simplify scoring & get rid of the 1 yaku hand minimum. It makes the game a lot more fun for people who are new to the game.