I am going to pitch another idea I have no time to GM myself, but I hope someone else will take it up.
I would like to play in a game loosely based upon Conrad's book. Essentially a small group of warriors and mercenaries will be tasked with killing a man who has proclaimed himself a God to an indigenous tribe and may or may not possess actual magical/supernatural powers.
The game would entail their trip to the City in the middle of a perilous jungle. Think Mayan architecture in terms of the design of the place. The story would take place in a fantasy world, but would not include any magical elements (beyond the possibility of their target having magical powers) or non-human races. The technology level of the group should be similar to 10th century Europeans.
I'm thinking 3-6 players, with the GM playing all necessary NPCs and antagonists, as well as mapping out the challenges they will face both in the jungle and once they reach the city itself.