I'll go a game route: Mario Kart. It's just so perfect. All of them from the SNES to the Switch.
I've played countless hours and never get bored. The level designs are all so interesting and unique I find myself discovering something new every time. It's social and I've seen it dominate dinner parties.
I'll second pretty much any old rice cooker with only one button design. There's a reason every Asian home considers it integral.
More than just rice, you can do so much more than one would think in there. I cook a Spaghetti Squash by just placing it inside on warm. No oil or anything. Then I go to work, come back 10 hours later and it's perfect. Can open it with a butterknife.
I'll take it over a slow cooker any day because it can set to a boil. The warm setting is perfect for most things and I've used it to make stocks, confits, yogurt, stews, curries and eggs without worrying about burning down my kitchen when I'm away as it will set itself to warm when there's no more water to evaporate.
I've played countless hours and never get bored. The level designs are all so interesting and unique I find myself discovering something new every time. It's social and I've seen it dominate dinner parties.