I've just had a campaign idea that I'll never, ever get to run because I don't have time, and neither does anyone else I know. Ideas ripped off from everything, as usual, but eh.
I'd start out with the FF6 campaign I've mentioned before, and not tell anybody of my true intentions. Right around a confrontation with Cid in the Magitek Factory, the party will be interrupted by the intervention of a time traveler, who insists that Cid's survival is necessary for maintaining some sort of timeline stability. Thus begins the struggle against what turns out to be a city-sized military research facility whose central AI is manipulating history to ensure its own eventual construction, and the party eventually either wins or reaches an understanding (along the way acquiring access to highly advanced technology), only for an unpredicted meteor shower to devastate the general area. From the craters would come many explosions, and the sound of metal clanking on metal, and finally the battle cry - "WAAAAAAAAAAGGGGGHHHHH!!!!!!!" As the party fights back the Ork invasion, it eventually comes to light that they are all descendants of Human nobility, lost in a Warp storm as infants - and though they are initially victorious in battle, they cannot fight back the unstoppable tide of Orks, what with that whole reproduction-by-spores thing. They are saved by Imperial forces, and it is soon revealed that the world's moon is, in fact, an ancient weapon from the Dark Age of Technology*, some sort of planet-destroying battlestation. The party may use the preposterous variety of technology now at their disposal to save the world somehow, or just fire the weapon and destroy the world. After many adventures beyond the furthest stars, they will eventually find themselves battling into the heart of Holy Terra in an epic assault that culminates in the Emperor's true death. His spirit will instantly reincarnate, push back the forces of Chaos, save humanity, and as, thanks to the party, offer them a choice. They may choose the red pill, or the blue pill.
I don't really know where to go after that one. Also, it should be noted that I don't actually know anything about Warhammer 40k.
*Or whatever would be recent enough for it not to be heretical, but to be unusual.