Well, I have to say "all the above" as well. I've run fantasy on The Orb, science fiction with savaged Mutant Chronicles
, and horror with The Babylon Working
My most recent campaign is a time/dimension hopping slugfest against the minions of the Elder Gods; however, two characters are now working for Nyarlathotep in one of his many guises, but this only happened after the following:
The PCs encountered Mi-Go and a teleportation device in the California desert during 1928. This led them to Xochicalco in Mexico and their encounter with the minions of the dark god Nyarlethotep. They tried to stop the "operation" taking place in the ancient ruins and accidently damaged a time/dimension gate and set it off, causing them to be "swallowed" by a time worm.
They were transported back to 117 AD and the Roman Empire. There they learned Latin, made money in the arena, and eventually gained employment with a wealthy collector of antiquities who sent them off to recover lost artifacts that should have already been sent back from Britain. This led to their discovery of the legends surrounding Joseph of Arimathea, the Staff of Thorns, and the Carpenter's Cup (Holy Grail). They eventually fought the Cornish giant Cormoran and his wife Cormelian (with the help of a young Dumnonii tribesman named Jack, of course
) as a means of gaining entrance to the top of St. Michael's Mount. There they entered a Doomesque structure called "Hell's Cathedral" and battled creatures from the underworld to gain the Cup. After fighting off time-travelling Nazi Nordics (members of the Thule Society) who had arrived just moments too late to stop the party, the archangel Michael appeared to the PCs and explained that their help was needed if man was to avoid an eternity of suffering. He told them to "purify" the Well of Ur.
The party recovered one of the Nazis' Time Spheres and used the dark technology to travel to ancient Mesopotamia. There they overcame incredible odds and used the Holy Grail to purify the Well of Ur and end the magical distortions across the dimensional fabric separating the million worlds--these disruptions had been facilitating the dark gods return. There were several PC deaths during the attack on Ur-Nammu, but a small group of survivors was able to escape in the Nazi sphere just as more Nazi Nordics and an SS sorceror arrived.
A failed repair roll by the Weird Scientist landed the party in the Deadlands setting, circa 1876 in Tucson, Arizona. Players of deceased PCs picked up new characters there and they soon began a war against Bayou Vermillion. There was more time travel insanity as one PC insisted that the group use the sphere to go back in time to save his family from a slave revolt that had occured on their plantation some 20 years before. During this fiasco, which backfired on them in terrible ways, they met an aspect of Nyarlethotep who told the PCs they had interfered enough. He forced them back into their time/dimension sphere and manipulated the dark technology to dump the party on a beach in 18th century Australia; the sphere ended up damaged beyond repair.
There they met Captain Cook who had beached his ship, Endeavor, for repairs and had sent out a party to look for food and fresh water. Only half of the party returned, and all of those were screaming gibberish about dead men and a horrific ruin not far inland. The party investigated the terrifying catacombs and barely escaped with their lives. A wave of zombie fever broke out and the crew was nearly halved before the PCs could get it under control. The Endeavor left Australia with barely enough sailors to see her home. After several mad adventures, the party ended up in the New World, in Mexico once again. There, at the altogether unruined city of Xochicalco, they discovered conquistadors armed with high technology, including an airship armed with a lightning gun. The party annihilated the invaders (who were working for the big "N") and took the dirigible. The crossed the continent and started back across the Atlantic toward Europe; that's where they encountered a fog bank and a crying child's voice, then the storm hit...
The PCs have since been on Caribdus, doing all they can to save the drowning world. Nyarlethotep has since revisited two of the characters and has convinced them to help him. Interestingly, "N" wants the world saved, too. At least that's what he says...
Yeah, I know its weird, but we've been having a pretty good time. I can't tell you why "N" has tolerated the PCs--my players may read this--other than to say that evil may not be at all what they expect.