As I was saying, insects.

From the time when I was young I've heard the euphemistic old wives' tale that if humans ever launch an all-out nuclear self-extermination, cockroaches will survive, such is their resilience and adaptability. The logical continuation of this thought, of course, is that those same cockroaches will eventually evolve sentience and psychic powers, and will brutally subjugate the entire planet under the domination of an evil cockroach empire. The other insect survivors (your scorpions, your spiders, your bees) must, of course, band together to destroy the cockroaches. Give that some cool 3D graphics and a randomly generated setting, and you got yourself a game, baby. If I ever get back into gamedev (the pendulum is swinging again, I've actually coded in the last couple weeks) I might take a whack at it.