This is the one!

I've tried a bunch of to do list apps, but none of them had the feature that Any.do does - the integration with a calendar (recently added for iPhone and coming soon for iPad). I want to see my day with both schedule and tasks. You can go this with Google Calendar on a laptop, but my primary devices are phone and tablet. This app is simple, has a nice interface, and the all important calendar integration. Highly recommend.