Durarara!!, in one run-on sentence.
Okay so it's by the guy who made Baccano!, and the studio that animated Baccano!, so it's kinda like Baccano!, especially the OP, except it's in modern day Ikebukuro instead of a train and has an extra exclamation point, and also the headless horseman is there, except instead of a horseman, he's a biker, and he knows bike fu, and he's got this big goddamn scythe made of smoke that comes out of his neck or something idek, and this one dude apparently likes to throw vending machines, and there's some random instant messages mixed in there for some reason, not sure why, but it's got a bitchin' soundtrack and it's basically pretty awesome and you should see it if you haven't yet.