This funding scheme has great potential to reinvigorate the RPG genre.

In order of preference for an Obsidian Kickstart IP:
1) Game set in the Planescape universe
2) If Hasbro are assholes and won't budge on allowing the (now defunct) Planescape setting to be licensed, then Arcanum 2.
3) Icewind Dale III? I would hate anything but D&D 3/3.5 rules though.