I've got a few ideas... (You guys all know I'm coo-coo for new takes on this game.)
First off is "The Luckiest Tourist EVER" game, where people take turns guiding a tourist named Twoflower around a "small island" world as a tourist that always survives his excursions. Players also build "scenic detours" so that eventually the island will be filled with "quaint native attractions".
Secondly is the "Iron Chef" succession game where people build fortresses right next to cities, with the sole purpose of creating expensive and rare drinks and "prepared foods", to be sold afterwards to a shop in the city which becomes a restaurant or pub famed for its exclusive food and drinks. The game then becomes one of adventurers journeying to each exclusive pub with enough in trade items to purchase and consume one of these delicacies before moving on to the next one - a pilgrimage for food.
Thirdly, there's the community game where every dwarfed player chooses what their dwarf will do, and the person playing the game just makes seasonal updates. In the "Lonely Mountain" embark I tried to set up a proper dwarven economy, but the game was paused by Christmas, and I got limited pleasure out of all the bookkeeping...
Fourthly, there's the "Build a city" game, where using nanofortress, each player in turn builds a 1x1 "district" or "city block" of a great dwarven city, with the proviso that each embark is adjacent to one that came before (except the first one, naturally.) The one I'm currently hosting happens to also be using "Embark Everywhere" to situate the city blocks in a necropolis of thousand year old tombs. ('Cause that's not gonna cause bad stuff to happen - building your homes on old, sacred burial grounds...right?)
Fifthly, (I'm pretty sure that's a word...), There's the "Eight Squared" game where two groups of dwarves compete to rule the entire world in using a form of ritualized warfare that incorporates towers that look suspiciously like chess pieces in a world that just happens to resemble a chessboard. There are two tiers of players - the "Kings" of either side who order towers built or abandoned and the rest of the Players who try to fulfill these orders from "on high". (Pretty much, each move in the game involves either sending an expedition into an "empty" square, to build the new tower/piece for the chess move or to order the capture of an opponent's tower by an adventurer and his followers - getting to the highest level and taking a screen shot would probably signify a "capture" - then having an expedition build a new tower of the proper type to end that "move". to order the appropriate tower/piece to be built on a 1x2 embark adjacent to an opponent's tower with the double duty of killing or capturing all the opposing dwarves in the tower that was originally there. (This would be the chess move of "capturing an opponent's piece".)
Sixly, there's my "Minecart Tycoon" game utilizing a series of embarks to create a "Trans-continental mine-track" on a large map of North America turned into a df world map in Perfect World.
Seventhly, there's a game I've been considering off and on, where Players begin as the very first dwarves, with only a knowledge of herbalism and mining. Every time one gets a mood, the Player can choose for the race of dwarves to gain a new skill, and the workshop that goes along with it. I've often wondered if artifact blueprints couldn't come out of a "mood", that describe an artifact to be built using the randomized materials needed for the artifact. Then, dwarves could endeavor to build the useful ones, using the blueprint as an integral component. However, I don't think it works that way. Anyway, "Dwarves at the Dawn of Time" sounds like a fun game, and the entire history would be generated from there forward.
So - those are my contributions to this list. numbers 1-4 are all in the same world and save-file, (The Luckiest Tourist EVER) - which also has a tower full of pyro and aero and necro-mancers who happen to be an in-game guild of geomancers and map-makers.