I go 28 hours somewhat regularily whenever I'm trying to get back to a regular sleep schedule. Of course this never works, after a few days I'm all fucked up again.

My longest is probably between 44 and 48 hours during maneuvers when I was in the army. Lack of sleep combined with no food and extremely low temperatures leads to some funny hallucinations - I once radioed in "a company of midgets is approaching our position". Another time I fell asleep while standing and talking to another member of my squad. Yet another time I woke up lying on my back with a snowmobile on top of me - the driver had lost control and flipped over while I was sleeping on the back of it. They thought I'd passed out, but I was just pushed deep into the snow and didn't feel a thing - I just kept sleeping.

Ah, good times .