I once marathoned Tengen Toppa Gurren Lagann in one sitting. I skipped episode 16 (the recap episode), so it was something like 9.5 hours. (I skipped most of the OPs and EDs).
Though for manga, one time I totally NO-LIFE'd Bleach (when I first started reading the manga) and read something like 300+ chapters in one sitting. I don't even know how long that took me. I'm guessing it was at least two full days, but I'm not sure. Might have been longer. Time kinda blurred together at that point.
