I'm not sure how obscure/well-known this is, but I remember playing it as a kid and never hearing anything about it since, so...
The NeverhoodIt was an adventure game, but a really strange one: It was all done in claymation, for a start, and there was very little dialogue throughout... And it also had a great soundtrack of all this dixieland jazz stuff. I remember it as being kinda hard, so I didn't really get far, but it was still so weird and cool that it always kinda stuck with me.
Anyway I'm downloading it again now, so I guess I'll see whether the childhood nostalgia pays off.