Gimme Skelter is a horror alternate universe fanfic by The Angst Guy and Brother Grimace.
In 1969, Jake and Helen are inducted into the Charles Manson "family" and bring with them the Lance of Longinus, allowing Manson to actually enact his insane fantasy of "Helter Skelter": a race war that will leave only the 'Family' alive with all black people as their slaves. Every non-black person on Earth outside his cabal instantly transforms into a raging zombie.
In 1999, 1st Lt. Michael James Mackenzie of the Free Christian Republic of Texas volunteers for a mission to the California wastelands in search of a girl broadcasting in Morse code, claiming she knows what caused the apocalypse and how to stop it. A girl named Daria Morgendorffer.
It won four awards in the 2009 Daria Fanworks Awards: Favorite Overall, Favorite Melodrama, Favorite Science Fiction, and Favorite Supernatural or Fantasy Horror.
Due to scenes of violence, this should be considered an 'R-rated' fic (but you could guess that from the description!)
- There are several appearances by non-Daria characters: Mack's comrade on his mission is a version of Huey Freeman from The Boondocks; Raven Baxter from Disney's That's So Raven gets a background mention; a General Bradley is revealed to be Marvel Comics' Isaiah Bradley, an African-American test subject for Captain America's super-soldier serum (and the Lance of Longinus as something Hitler once had comes from Marvel's excuse for why the superheroes didn't despose him).
- The state of the rest of the world is mostly unmentioned, in part because of the lack of communication. Despite the characters referring to the 'zoms' as white, Kyle Armalin refers to "nine-tenths of the world" being transformed. There's mention of "the citadel cities east of the Mississippi" such as Cleveland and Detroit, under permanent siege from the 'zoms'; the Carribean nations are still intact and trade with Texas; US forces stationed in Britain regrouped at the Channel Islands; and the Republic of Zimbabwe (formerly South Africa rather than Rhodesia as in our world) is considered by Texans as the only other nation of consequence.