What's the last game you played for hours without breaks?

I was playing Call of Duty: World at War on Veteran difficulty, first day had me go for nearly 3 hours, but the next day had me going for 6 hours straight.

Body ached like crazy afterwards due to accumulating stress levels and so on... But yeah, as soon as the credits started to play, I noticed that the sun wasn't shining anymore and that it was already 11:56 PM... Just lucky that I was able to get enough sleep for class the next day.