In honor of April Fools' day, game maker Nitroplus has brought togther 14 anime, light novel, visual novel and manga incarnations of Lovecraftian evil, mostly chaos god Nyarlathotep to do battle in fictional strategy RPG Konton Taisen - Thousand Confusian Wars. It'll be out for the 3DREAMSTATION LL when the stars are right.
Nyarko-san - of course
DYN Freaks' Chaos Knight
Nyarlathotep from Alicia Y (Juan Gotoh's Jack the Ripper/Lovecraft series)
Kouyoku no Soleil -vii’s World-
sonaniru - what's a beautiful memories' Ticking Man (an evil that Thomas Edison unleashed on the world in an eroge game that drew from Wizard of Oz and Alice in Wonderland)
From the same, The M (aka James Moriarty)
Cain Murasame from Kentaro Yano's five-volume series Jashin Densetsu
Nobutsuna Kamiizumi from Shūmatsu Shōjo Gensou Alicematic
Christian XX's Hiraga Gennai
From Phantom Bullet
From Hiro Itou and artist Gyo's The Devil Doesn't Pay Me the Rent
Lulu from Mahou Shoujo Pretty Bell
Creeping Chaos from Wild Arms
It even promises (possibly eroge) CG that will make you lose all sanity points!
Meanwhile, http://nyaruko.com/ has its own April Fools' splash