Children is an experimental "art house" game that lasts only 30 minutes or so, so I kick it off by saying that you just have to play it if you are willing to deal with that kind of thing . But I find myself thinking about it more than the other games on this list. The appeal lies in how you interpret it, and then I like to think of it as a kind of old-fashioned Rorschach test.
It's a theme, though: Kids is an open comment on the crowds and how they behave. In a scene, the mouse swings over faceless shapes around a hole and sees when they jump in. In another, you get them all to choose a particular person. In another, are you leading a body with … which looks like a digestive tract? Trust me, it's all very strange.
Kids is not a traditional game, and developers Michael Frei and Mario von Rickenbach are cautious about calling it a "short interactive animation" instead. It is even part of a travel art exhibition. But if you are the kind of person who likes games that break from the boundaries of the known ones, consider that three dollars have been spent well.