Lexicon: an RPG, the creation of Neel Krishnaswami, is a game in 26 letters, where the PCs play the roles of opinionated academics composing an encyclopedia.
Here are two games of Lexicon, both running on Wikis. One is based on Nobilis, the other is based on Paranoia, and instigated by Alan Varney, one of the writers of Paranoia XP.
[ link from Ogre Cave. ]