Giveaway Plug-in

Does anyone know of a good Giveaway plug-in? One where people have to log-in and then can click a button and the code automatically shows up and gets emailed to the user?

Just like this one: http://mmoatk.com/mmo-giveaways/guns-and-robots-in-game-item-giveaway

If anyone has any ideas or knows of that plug-in, let me know!