Mekton from R. Talsorian Games has always had a default setting called Algol. The setting is essentially a showcase for all kinds of 70s and 80s anime concepts. It's an Earthlike world but with oddities ala Super Dimensional Century Orguss or Super Dimensional Century Southern Cross. There is Gundam-like mecha, psionics, reptilian alien bad guys, lost technology, wandering mecha nomads, technopriests and of course big, brightly-color anime hair. The game has gone through several editions, but Algol has remained as the stock setting for every one of them.
Algol was settled by refugees from an intergalactic war against an alien race called the Aggendi. The Aggendi wiped out the colony and left, thinking the job was done. The survivors, blasted back practically to the Stone Age, eventually rebuilt and spread across the planet. As the centuries passed, two large nations evolved, one on the northern continent and one on the southern - the Elarans and the Kargans. The archipelago of islands across the equator held a number of smaller nations, mecha nomads called the Etarrans, and the sub-continent of Muria. The egalitarian Elarans were descended from the relatively peaceful descendants of the original civilian scientists, doctors, teachers, etc. The totalitarian Kargans were descended from the colony ship's crew and military contingent.
Eventually, two things were discovered: the secrets of technology locked away in the remains of the original colony ship and that Algol was undergoing an ice age. The two nations began to jockey for land in the warmer archipelago, and a series of wars broke out between them - either directly or through proxies in the Archipelago. Once the secrets of the Mektons that were once used to defend the colony were unlocked, it was totally on between the two nations.
There's a whole lot of awesome in the setting. The inhabitants live in arcologies, connected to one another by fortified elevated roadways, for protection from weather extremes, the local wildlife, and enemy attacks. The Murians fill the role of mysterious technopriests - almost like Atlanteans - with their high technology, psionics and all encompassing force field that keeps everyone out. The appendix in the original Mekton book included all kinds of neat descriptions of various arcologies, personalities, and creatures.
It shouldn't need to be said that the biggest piece of awesome in Algol are the mecha. The Mekton Techbook expanded on the original build system for Mekton II and made it in a fantastic, flexible system and at the same provided a Jane's Fighting Mecha of Algolian Mektons. In a clever move, the listed mecha start with basic models (the biplanes of Mektons) and move forward in time as technology improves. Even better, the descriptions of each Mekton provide vignettes into Algol's history by mentioning battles, personalities and other events. The drawings of the mecha were done by Jason and John Waltrip, who have also done art for Car Wars and Robotech: the Sentinels and other comics.
The setting even got the anime-series treatment in the form of the Operation Rimfire campaign. I still regard Operation Rimfire as one of the best campaigns I have ever run. Basically, you played the crew of a spaceship constructed solely for traveling to Algol's outer system to investigate an anomaly. The book itself was gorgeous, with great art and full color glossy pages giving character backgrounds, maps, etc. Unfortunately it was soft-bound, so the pages eventually started to fall out. As can be expected from a pre-published adventure there are rail-roady parts and pacing issues, but it had a good mix of character development and action, a few twists, and a suitably dramatic big-boss ending.
Mekton Zeta, the last edition of Mekton, expanded upon the setting by using the end of Operation Rimfire as a launching point. It described the rest of Algol's star system and the new bad guys - the returning Aggendi, which it retconned from saurians into a kind of insectoid species. The technology base for the mecha was also advancted. Unfortunately, a lot of the accumulated material from previous editions was either paraphrased or left out, so the Algol presented in Mekton Zeta seemed a little bland. The example mecha designs for the Algolians weren't quite as interesting, either.
I have extolled Mike Pondsmith's virtues before, and the Algol setting is further proof he's a master game designer and story teller. Pondsmith manages to meld many disparate influences together seamlessly and organically, polishing them into a really fun setting with a lot of gaming potential.