batman : Arkham asylum - properly the longest game, oh and as this will count for all games mentioned below, i define "one sitting" as "one day", bathroom breaks, phone calls, dinner and such are all things i cant avoid and cant do from my chair.
portal - well duh.
the secret of monkey island : special edition - i played the original so some of the puzzles where in the back of the head.
braid - to beautiful to look at and listen to, i couldn't leave it.
machinarium - same, but times 2.
Prototype - hur hur blood.
plants vs. zombies (and almost all popcap games) - aww look at that, THATS SOOO CUTE!!
CoD world at war - rushed true all the American missions and replayed most of the Russians.
and there where a bunch of others but its been so long ago they are no longer interesting enough to write down.