I'm writing a short story today. The entire thing came to me last night in bed, almost fully formed. It will be down on virtual paper by sunset.
Update: 45 minutes in, and I'm already at 1,000 words.
Update 2: 12:30 pm and I have 2,250 words, including a 30 minute break. I might not finish in just one day if I burn myself out. Not that it would really be finished anyway, with the editing process still to come. But I would like a rough draft.