Good question! When I first came up with the idea of a world war in the Gamma-verse I figured it would be set in the standard 200+ years in the future that was the basis for the original Gamma World. But then it seemed like an infinitely swappable idea!
Remember that Gamma World War is made of (at least) three sides: humans, mutants, and aliens. Here's a few other variations on the theme that could easily be implemented for other eras:
Atlantis, Post-Sinking and/or Volcanopalooza
Mythological mutants, Atlantean centurions manning
Archemedian Death Rays vs.
Ancient Aliens! I'm thinking the E.T.s were the ones that destroyed Atlantis. Now the Atlantean diaspora (pre-Romans, Greeks, Mesopotamians, Sumers, everybody basically) has begun and the descendants are battling all manner of Greek mutant tragedy in order to survive while the ancient astronauts from Zeti Persei continue their raiding parties in an effort to reclaim their former colony world. Sword, sandal, and saucer epic in the making!
Weirdest World War
This one's obvious. US has the bomb. So does Japan. So does Germany and Russia. The Cold War never happens because it instantly went hot! Mutants! Giant lizards!! Roswell Aliens!!! A hot fudge sundae of WW2 battles, swirled in with the best parts of Indiana Jones 1, 3, and 4, plus Flying Saucer, Godzilla, and Ray Harryhausen films from the 50s and 60s.
Can't forget a heap o'
The War that Time Forgot and
Weird War Tales thrown in for good measure. Grease guns meet gamma rays. Call it "World War Doom!"
"High Doom" Meets the "Treasure of Gamma Madre"
Cowboys vs. Aliens vs. mutated miner-49ers who find uranium in search of a gold rush. A wave of irradiated zombies spreads just as invading wagon trains wielding gas-powered ray carbines are settling the West. Steampunky Thundarr-like techno-warlocks Edison and Tesla quibble from their electro-hoversleds, sending wave after wave of giant armored jackalopes into battle. Cowboy centaur Wild Bill Hickock fights off Planet of the
Bison-like minotaur men! (Hat tip to One-eyed Bob!). Seeing their chance to claim jump the Earth's rich uranium, the aliens show up to set up their own mining operation--and put down those pesky humans.They of course are familiar to the native tribes, they're the original
skinwalkers!
Irradiated Oni and the Robotech Ronin
A meteor strikes Mt. Fuji in medieval Japan leaving a wake of destruction. The mountain erupts and spreads strange mutagen across the countryside and awakening the Gods of Old a la
Princess Mononoke-style.
All of the Orient's mythologies of Oni, animism, and spirits are made real, and wreak havoc on he remaining un-mutated humans. After the shoguns fail to protect them, the peasantry and remaining samurai make their last stand--when a
Zentradi starship crashes off-shore.
What seems like a disaster-and-a-half is a blessing in disguise as the ship is empty but a windfall of alien tech. Can the humans salvage--and comprehend--the alien
robotech well enough to fight off the mutants? And will they be prepared when the hostile giant-sized Zentradi come sniffing around for their crashed cruiser?
Far-out, Far Future
Think
The Time Machine meets the
Herculoids. Here, the Earth is older and returns to seed with newly evolved megafauna and mutant Morlocks feeding off the pure-strain human Eloi. It's also got yer standard weird Herculoids planet Quasar of the barbaric far future. The aliens? Humans from the distant past!
For the aliens: hordes of
lunar Nazi's (that have been hiding out in secret bases for eons) depart a broken moon to launch a blitzkrieg on the savage Earth. Can the canibalistic Morlocks, rayrifle toting Mutoids, and slingshot-lovin' Eloi overcome their food-chain issues long enough to turn back the 333rd Reich?
Arrak-a-pocalypse
So Arrakis--
Dune [dramatic pause] desert-planet--is basically
already a post-apocalyptic setting. Let's play with the knobs a bit and see what we come up with:
Fremen are mutants. They're former humans who were altered by spice. The more direct-spice exposure, the crazier the mutation. The more sandworms you wrangle, the more metal \m/ you become, dialing up all the way to full-on sandperson-from-Star Wars mania. They're suspicious of anyone trying to take anything from Mother Dune. They're full-on, crazy-in-love with the planet and consider themselves it's protectors and martyrs.
Valids/pure strains are House Atreides humans who are doing their best to mine the spice without incident. They're the survivors of the last mining colony that was abandoned here about a century ago. Most of their tech is broken, outdated, and considered "magical" by the Fremen. Pure humans stay that way by wearing
stillsuits to filter out the spice. Yes, there's the potential to becoming a mutant if you don't keep yours intact or working properly. The Fremen mutants are not happy about any of this.
Aliens are faceless Saraukar assholes who are bent on taking over the universe. Under their masks they're a mass of plastic skin, tubes, and organic electronics. They believe in shooting first, second, and last. They have a spacefleet ready to hoist entire sandworms onto their space carriers and take them back to Giedi Prime where they'll be juiced like Florida oranges for their extracts. They'll kill a pure-strain just as quickly as they'd kill a mutant, so both have a reason to hate these dudes.
Anyway, just a few thoughts...
*I totally reserve the right to revise the post at my leisure!