This is a campaign idea I've had kicking around for a couple of month that I'd like to run, but would much rather play in!
The Lamentations of the Flame Princess Weird Fantasy RPG
One of those epic Chaosium world-sprawling Call of Cthulhu adventures such as Masks of Nyarlathotep
And run it like a D&D game, with the time period being sometime in the 16th, 17th or 18th century.
Now I gotta see if I can find a copy of the 2e "A Mighty Fortress" sourcebook ...