This is just an idea I've had rolling around in my mind for a bit, and it's going to be a mix between two concepts I've had for an RP.  The basic idea is that each character is one of an absolutely minuscule number of people who survived the new ice age brought on by an asteroid impact that blocked out the sun for over a month, causing the Earth's climate to change dramatically.  It is now ten years later, and you are one of MAYBE tens of thousands of people who have managed to stay alive in the snowy/icy wastelands.  It's going to be a bit like the book World War Z in that each character has their own story, completely separate from anyone else's.  If you bump into someone else, you bump into someone else.  Maybe you stick together, maybe you don't.  The most important idea is to focus on the isolation and abject misery one might experience.

Obviously, it's just a rough idea right now, but I think it has potential.  I have a feeling it won't get a lot if interest since there's not going to be a lot of (if any) character interaction, but there will be a lot of individual freedom to do whatever you want in the RP, within reason.