iOS (jailbroken): Do Not Disturb is one of the best features of iOS 6, but you have to jump through a couple of menus to toggle the setting. Flusterless is a tweak that adds a small toggle to your phone's lockscreen for easy access.
The whole point of Flusterless is to make it easier to turn on Do Not Disturb. From the lockscreen, you can slide the setting to the right to turn Do Not Disturb on and slide it again to turn it off. It's incredibly simple, and it's helpful if you don't feel like setting up schedules for your contacts.