What games were so good you completed them in one sitting?
I.e., games that hooked you in and you couldn't stop playing until it was finished. Not games that just happened to be unexpectedly short. And by "completed" I guess I mean the main story etc, not 100%ing the game :).
For me, it would be Catherine, Bioshock Infinite and Black Mesa (although I think I got to the final area then had to go to sleep and complete it the next day). I also played an ungodly amount of Hades in one sitting, but didn't get the "full" ending in one day.
I've always loved Half-Life, and Black Mesa really does it justice. Xen was beautiful, even if it was still quite frustrating towards the end. I bought it at the 1.0 release, would be great to see if they've added/changed things now... they seem to be really dedicated to updating it!