Welcome to a politics free rant. On games. Obscure roguelike games.
Starting from the start. Temple of the Roguelike is a great place to find roguelike games. Here's a URL.
Temple of the Roguelike
Guild: Guild is a party-based roguelike where you control four players. Pretty decent, though I'm only good with one character.
Guild
Powder: Powder is an excellent roguelike for multiple platforms, though there are better, its multi-platform support earns it a fairly high status in my book.
Powder
GearHead: GearHead is far enough off kilter to earn it an obscure title. You won't find it on Wikipedia, either. It's a sci-fi mecha roguelike. I'm an sysop on the wiki. You can find more info from there.
GH Wiki
Incursion: Incursion is an awesome d20 roguelike. Try it.
Incursion
Most of the Slashie.Net roguelikes: While relatively well known, most people probably don't know about them. They're mostly based off of other video games.
Slashie.Net
Yep, that pretty much winds it up. One bonus, though I sincerely doubt anyone really likes it: Omega! Omega's actually pretty awesome, but it lacks a lot of modern conventions making it pretty hard to play.
Omega (Windows)