Clear

Clear is a trendsetting app for design and usability. You'd have to look at their site to see the lack of features, but features done expertly. A must have for productivity.

I've had the benefit of using it for 3 years and it's my go-to to-do list for almost everything. I use Carrot for work because I love her jokes, but Clear is all gesture based, in the cloud; where you could write your grocery list on your desktop then check your phone when at the shops. Don't let the clunkier to-do lists take up more of your time.