Slambo, aka Slambo the Everchosen, aka Slambo, the First True Prince of Chaos, aka Slambo the Everchampion, aka Slambo, Age of Slam Commentator, aka Slambo, Chaos God of (desired portfolio) is a Warhammer Fantasy meme character.
Originally a Warriors of Chaos/Mortals miniature dating back to 4th(?) edition (earlier, he was pictured in AHQ). Older Games Workshop ads for models named some individuals despite the fact none would ever recieve lore. There is some artwork depicting him in Advanced Heroquest though. EDIT: The model actually originates from the original Hero Quest game and was the standard "Chaos Warrior"
During 2014, while /tg/ raged and lamented the changes in End Times, an anon decided to cheer the mass of Fantasy fans up by posting old White Dwarf promos in a nostalgiabomb (or a lesson for newer players). One in particular model, dubbed Slambo, caught the attention of the thread.
Slambo is heavily armored like most Warriors, although his faux-Viking helmet horns meet to form a halo like a medieval painting of a saint or king, while he is armed with two huge battleaxes. It was love at first sight for many.
Since then, Slambo has come to replace any Chaos character with displeasing lore. If Archaon is unsatisfactory, Slambo is the Everchosen with Archaon being some past failed twat nobody cares to remember. Those who dislike Be'lakor (the many that is) consider Slambo the first Daemon Prince, the master of Chaos Undivided. If a player wants an extra special Chaos Champion, Slambo is of course eligible. Those who feel Khorne, Tzeentch, Slaanesh, Nurgle, even Horned Rat to be boring little shits consider Slambo the true master of their branch of Chaos. When Age of Slam was first conceived, Slambo was the replacement for Jim and Bob as commentator.
2017 update: Slambo is back! (In resin, but still!) Now he has shiny green armor, and rules in AoS. He can even throw his axes. (The only downside is he can't take a Mark, which really would have been useful). White Dwarf March 2017 even published rules to use this mini in the "Warhammer Quest - Silver Tower" board game.