Every year several of the biggest players in the game development industry host the Global Game Jam. It's a 48 hour programming competitions. Groups of people all over the world get together for the challenge. On Friday night you are given a topic or idea or premise of some sort and have 48 hours to design an create a game based on that premise. Each game is judged based on several things including gameplay, art quality, and how close to the original premise that the game is. The winners receive a small prize but most people go simply for the challenge.
The first year at the Global Game Jam I went with a team of 8 people. The premise we were given was 'Deception'. Using that, the team created 'Lamb Mines!'. In Lamb Mines you play as an eccentric mad scientist who has cloned too many sheep and needs to get rid of some of them. Using two disguises the player must herd the sheep into mines which can be placed around the field. The Sheep costume attracts nearby sheep toward you, while the wolf costume scares them away. The deception is tricking the sheep to wander into the mines.
The next year, most of the same team got together again. Then were were given 'Inevitability' as the premise. Starting with the code we had written the year before, we built a game about being god and smiting the bothersome peasants that have taken up home on your island. Using a myriad of different weapons from a simple lightning bolt to summoning cataclysmic meteors, you must clear out the island before time runs out. Peasants are much like rabbits though, if left alone to long. Each peasant on the map will increase the spawn rate of more peasants. It is possible to win, but very difficult. The message is that even with the power of a god, sometimes things are just inevitable.
This competition is probably one of the most challenging things I have done. It relies on your ability to both create and develop from scratch within a very tight deadline. Stress is also quite a challenge in the development. Each person has ideas about how the game should be but not everything can be realized in such a short time.