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.
Plants Vs. Zombies!
My wife and I just sat there like… zombies… for the whole day and night until we finished it, and then went to bed surprised and happy when we got our musical reward at the end!
The Flash gaming era at it’s best.