How long does it take to complete the single player campaign in Diablo III on Normal difficulty? I have no idea, but it took Level 32 Barbarian Yoshichan 12 hours and 29 minutes to beat Blizzard's freshly released game. This NeoGAF post (thanks Eurogamer) shows off a final shot of the Barbarian character's stats.
Yoshichan (also his username on NeoGAF) explains how he accomplished this feat in such a short amount of time: "Frenzy baba with lots and lots of mobility and defensive skills – 415 dps unbuffed, ~700 dps buffed."
So where does he go from here? The next difficulty level, of course (did you think he was going to quit playing Diablo III?): "All right guys, wish me all good luck in nightmare!" he posted. "Going for it asap. It's actually starting to get warm in the bunker now that I think about it."
While we can't prove it (only Blizzard can), we believe he is the first person in the world to finish the game. He probably deserves to be in the next edition of the Guinness Book of World Records.