I have been trying to come up with a multi-world setting that mixes epic fantasy and science fantasy, and styled like an 80s cartoon (He-Man, Thunder Cats, Heavy Metal, est.), but a little more mature.
In this universe, a great galaxy empire fell, and world, after world is falling to the rule of evil warlords and sorcerer kings. Most of the worlds have fallen to barbarism, and its up to the PCs to stage rebellions, plunder ruins, conquer worlds, and so on. Most of these worlds are as small as moons, but they have earth-like environments (gravity, air-pressure, wildlife, est.). Like Star Wars, it would not be unusual to one or two climates or terrain types. Travel between these worlds are possible through large stargates, built before the fall of the empire. These gates are usually found in cities, and are built, so that airships can move through them. I'm still working on a core setting, as a springboard for further sandbox adventures.
As barbaric as this setting is, there are some fantastic pieces of technology still in use. Many of which are styled on A Princess of Mars, with airships, blasters, est. In fact, most of warriors look like the figures from a Boris Vallejo/Frank Frazetta cover - meaty guys with fur/leather loincloths and chainmail bikini-clad amazons, with leather straps around their naked torsos. The keystone of this setting - and as an excuse to show a lot of flesh - are battle harnesses with built-in force field generators (as pictured on the side). They work like the Holtzman generators from the Dune saga, in that they can deflect range attacks, while melee weapons can slip through but without the whole nuclear blast, from hitting it with a laser. You can carry conventional body armor, but if you keep the generator on to long, you will overheat quickly, as the barrier tends to trap in body heat if bundled up. I can list paragraphs of how this magical piece of Applied Phlebotinum works, but this is not a "hard sci-fi," and this is the best excuse to show near-naked warriors in a gun-toting science fantasy I have ever seen, so I'm not going even bother! Just enjoy the parental this setting has at making sexy pinup art, without if feeling like token glamor art! =D
Another problem, it to what system to use. I'm split between Barbarians of Lemuria and Mini-Six. I might use both. Like like both systems, and they both have their good points. I will post updates, as soon as I come up with more ideas. (WOW, this might have regular updates! Hell is going to freeze-over in a hand basket! ;P)