An interesting art piece that will have you going back time after time for various outcomes.
The Stanley Parable is an interesting piece of interactive software that originally started as a free mod for the Source Engine. You start in your office and almost immediately encounter a narrative voice that spurs you along a path. As you move through the environment, you are told to go one way but are given the option to head another. On first play through it lasted roughly 5 minutes where I deviated from the path of the narrator, defied his warnings about "heading towards my demise" and eventually ended up in a meta museum displaying all types of information regarding the creation and the art assets used in the piece.
The replayability surrounding The Stanley Parable is trying to discover just where your co-workers have disappeared to and how many different "endings" you can get from it, the larger realisation is the twist at the end that hits you after you've closed it down and headed off to do something else about your day.
Those who are looking for a "game" stay well clear; but those who are up to experience something unique and interesting should by all means give it a go. There isn't really much more to be said (without spoiling the game) but it's something that proves a quick and delightful experience.