Obsidian Entertainment, makers of many RPG's over the years, most recently Alpha Protocol and Fallout: New Vegas, are working with South Park creators Trey Parker and Matt Stone on South Park: The Game. Described as an RPG you are the new kid in town who has to save it from various threats.
The game is set to come out on PC, PS3 and Xbox 360 next year, and THQ are on publishing duties.