There's an old DOS game that I used to play a lot of which comes to mind, but I'm not sure if it counts as obscure. Shareware game with customizable levels, had ASCII graphics. Could have sworn I've seen an image from it recently, might have to dig it up.
I wrote an article on NetMonster so I could submit it to Hardcore Gaming 101, but then I couldn't get the thing running in order to take images. D'oh. It was a Pokemon knockoff, but instead of exploring the game world, you could put a NetMonster cage on a web page and players could find a monster from there. They could have custom images, and there was a random chance that they'd be a boss or miniboss. People actually kept records of where to find bosses and stuff and posted them around.
It's a relic of the Angelfire / Geocities era, so it seems like most of the old sites are gone.