Heaviest semester of my engineering degree - one of the design courses was being taught for the first time by a new professor. While the professor himself was absolutely amazing, the main part of the course grade focused on a design project which was very open ended. The group I was working with were slightly over zealous and took our design far, far beyond where it was intended.

Normally this wouldn't be an issue, but the project was given out in mid-November with the final presentation due the second week of December. The last week of the project our group virtually lived in a comptuer lab on campus - most of us averaged maybe two or three hours of sleep a night early on in the week, with less and less the closer we got to the presentation. I remember taking a nap in the hallway for a couple hours early Thursday morning sometime, but that was the last sleep until our presentation was over. Our material ended up being amazing, but the presentation was, erm, less than perfect. :)

Thoughout my undergrad, my birthday always fell the week before finals. Because I always took more classes than I should have, I pulled 24+ hour days on four of my five birthdays during that time.

The key for me was eating decent food on a pretty regular basis during that time... After I pass the regular 16-20 hour mark, I'd start having something to eat at least every 3-4 hours. Terrible on the body, but it worked like magic.

It starts gettin' weird above 48 hours though...

I swear by the Zebra M-301s. Several of mine are at least four years old and counting. I've never been able to find a .5 sized pencil as clean feeling as those.

Though I do have to have an extra eraser around to use with them. I like having a big eraser handy anyway though, so it's rarely much of an issue.