In all seriousness, you're going to have to pick a genre, pick basic characters, story arcs, and start putting them together. While it may be helpful to discuss various plot bunnies, character backstories, etc here, you may not get many serious answers in such broad questions.
With that said, I vote for an interstellar battle between two races of robotic organisms that spans the universe for several centuries before finally making it's way to the Milky Way. Think Transformers meets Borg (Star Trek) meets Reavers (Firefly/Serenity)