Spirit Island is a brilliant cooperative game by R. Eric Reuss which turns the usual colonize-an-island schtick on its head. The players are spirits of the island itself, struggling to throw out the colonial invaders. Save the island, you win. Let the island be overcome by invaders and blight, you lose.
It's been my most played game since I got it, and we've played it hundreds of times. Me being me, I couldn't help but tinker with it and make some of my own content. Here's what I've come up with—