Global Game Jam 2013
The first time I participated in a hackaton was the GGJ 2013 (Yes I am posting this about 1 year 4 months and 18 days later).
We had to develop a videogame in 48 hours and make it about the topic anounced. That year, the topic was one audio of a heart beating. So... we made the story of a rabbit that had its heart stolen by an evil rabbit (very original I think XD). And you are the rabbit in a maze and you have to find the pieces of your heart.
We used Unity 3D to develop the game and a lot of other software that i don't master :P (3DS max, illustrator, photoshop ...)
We even made a trailer of the game!
https://www.youtube.com/watch?v=QRXRdelQK_M
It was a great experience, thank you team (again 1 year, 5 mo.... later)
Here you can see the GGJ website and download the game if you wanna try it! (It's very difficult to play... only for "pros").