Genso Suikoden. Either you know what it is or you don't. If you do, I don't need to say anything.
If you don't, it's a series of three (soon to be four) Playstation RPGs. To sum up the plot of each game: 108 Stars of Destiny gather to change the course of history. Yes, 108. The Suikoden series probably has more characters than any other RPG series, since the 108 are (mostly) different from game to game.
I've only a single fanfic based on Suikoden for now; it can be found below.
Memory, Sorrow, and Thorn
The Scarlet Moon Empire is defeated, but the war with the Jowston Alliance continues, even as internal problems beset the Toran Republic. And at this critical time, President Tir McDohl slips out of Gregminster late one night... [Suikoden I]