As a major proponent of Checklists, I love how the Orderly App lets you create multiple To-Do Lists and organize your them by Work, Personal, Project lists. On top of that, you can smoothly drag these colorful lists from High, Medium and Low priority. What seems very intuitive is most likely how our brain processes information, done in a visual manner.
Their motto is: "Orderly is the most natural way to create and manage to-dos using simple iPhone gestures."
Download it from their website here: http://orderly.tektontek.com/