This might sound pathetic, but i've once spent an entire day trying to break a Nintendo Power lap record in Diddy Kong Racing 64. I've played alot of games non stop for several hours, but this reached obsessive levels lol.
With bathroom breaks:Resident Evil 4. When it was first released I ended up playing it on GameCube for ten hours straight. Didn't really help that I had school the next morning, so I slept through nearly all of my classes. But damnit it was worth it. RE4 > Algebra.
Without bathroom breaks:SmackDown: Here Comes The Pain. Played this for about three-four hours I played this game until I un-locked everything. This was more of a case of OCD where I knew I was close to, so I had to finish the game.
When World of Warcraft: Wrath of the Lich King came out, I seriously put about a legit 40 hours straight into that shit. I remeber the horde and alliance had a "mutual agreement" not to PvP during the launch. Well somehow that fell apart and by the time the Horde (who mostly agreed to start in Borean Tundra) and the Alliance over in Hyjal bean merging into the Dragonblight, shit hit the fan and massive PvP began around the Dragon tower area for hours on end. I was all hyped up on coke and Mountain Dew. What a great series of nights.
I'm so glad I quit WoW after Cataclysm. I kinda miss it for Battlegrounds occasionally, but then guilds call for raids, grinding out rep, dailies, etc. Shit consumes your life.
About 2 years ago school was called off due to a lot of snow so I went home and played Gears of War 2 from 9am to about 1am including snack breaks and toilet breaks of course. I could probably last longer than that just need to find the right game.