When I was younger I used to be able to stay up for days. Especially during nights before I was going on a planned vacation to a theme park and so on. Also, when I would get a nice new video games. If it involved multiplayer, I often stayed up all night playing it. I've actually fallen asleep playing Halo and Final Fantasy XI.
On a serious note, when I used to play Final Fantasy XI, I would go to bed somewhere between 4-8 AM, sleep until the afternoon, and do it all over again. But like I said, this was when I was young and didn't have a job, bills, etc...
Uhhh... probably about 2 A.M. in the morning. Although it's important to note that there have been nights I've gone to bed earlier than that, but gotten up really freaking early in the morning. it's a greater loss of sleep, even if I didn't go to bed as late.
I also regularly stay up until 1:30 A.M. (and sometimes about 2 A.M.) every Saturday night. Mainly so I can stay up to see new episodes of Bleach.
Let's see.... Ahh. I was on a day-trip to France with my class one time, and it required us to catch a coach at 12am (so we would have the whole day there and arrive back at about the same time). So after a normal day of high school, we all went back at midnight to get on the coach, and I spent the night playing Mario Kart DS with several people and counting large mail and stationary vans against my friend... then we travelled to various villages and shops that day, returning the next night... I remember the only sleep I got was a 30 minute nap while sat around the coach in the Channel Tunnel train, man it was so hot in there. Rofl I laughed when some of the boys fell asleep in eachother's laps o_o
So... that was around... 36 hours with only a nap, but I'm not doing that again any time soon- I slept until 3pm the next day o_o
My sleep pattern's kind of non-existent anyway, on normal nights I end up going to bed at 1am, and on some weekends at 3-4am. Yet all I do is sit there watching stuff on the internet, or talking, or playing games. o__o
...Although since ST comes out on a friday over here, I'll probably end up pulling an all nighter without meaning to on that night xDDD