I've talked about this concept before once or twice, I think. My last Greyhawk campaign will soon reach the End of All Things. This particularly games features the gestalt rules from Unearthed Arcana now runnig at a staggeringly high level, like above 20th. My next lengthy campaign will be an Eberron-based affair not using gestalt classes and starting at first level. So in between these 2 campaigns I want to run a short game of something else entirely, to shake up the neural pathways of all involved. I don't want me or the players coming into a new 1st level game with all the habits learned from epic-level awesome-osity.
At first I knocked around running a giant robot game of some sort. But the juice just isn't there right now. So my new idea is to go with Classic Traveller running one of the old modules. My first go at a Traveller game was a slow-motion trainwreck, but I'm positive that was all on me and had nothing to do with the rules. I'm ready for a second shot and the players have their act together in a way that could really make Traveller sing. Now I just need to pick an adventure. At first I thought Adventure 4: Leviathan would be neat. In it the players get a big shiny mercantile exploration vessel. They recruit (read: roll up) a crew and set out to open up new markets in the uncharted regions rimward of the Spinward Marches. But we just got this dirigible in Jon's campaign and my Eberron game will focus on sky piracy, so now I'm thinking I need an adventure that focuses less on zooming around in a spaceship.