It’s not super obscure, but I think I’d have to go with Star Tropics. Gameplay wise it’s very similar to Zelda, but the setting and story is more like EarthBound. Interestingly the game is a first-party Nintendo game that has never been released in Japan despite being developed there. Another thing is that it’s been almost completely ignored by Smash Bros. I think it got a mention in Brawl’s chronicle, but that’s it. Even Ultimate forgot about it despite having all kinds of deep cuts among the spirits.