RPG IDEA #1!11!1. Avatar: The Fires of Invasion (as in, the Last Airbender-Avatar. Not James Cameron-Avatar.)
Cut for length.
RPG IDEA #2: DC Superhero/Supervillain RPG
Whether it's the animated universe or just the DC universe in general, superheroes and supervillains galore! No real plot thought up yet. I might sign up as Poison Ivy and cause some general mischief to get the ball rolling, and you super villains out there can run with it! I mean, that's your job as a super villain, right? Blow shit up? Possible inclusion of Marvel characters, for those who hate DC? Let's just... not worry much about the little details about making that feasible.
RPG IDEA #3: Greek Mythology
Whether you play a Titan, an Olympian, a demigod, or mere mortal, the world of Greek mythology is always fun to play with. I can see this going the way of Herc or Xena given our RPers - part serious drama, part comedy. It's Greek mythology, after all. It's fun to mess with.