As someone who needs to-do lists of her to-do lists, it doesn't take much to get me excited about an app like this.
The Wunderlist app, available for Android, iOS and Windows, helps you stay on top of all your tasks through the creation of lists that you can then manage from any device as well as share with other people.
From your grocery shopping list to important business details or overseas travel plans, you can add anything you want and have a number of active lists on the app.
You can also set recurring tasks as daily, weekly or monthly to-dos, create sub-tasks (lists within lists - an OCD person's paradise!) and due dates. You can also print your lists, get reminders and notifications to make sure nothing goes undone.
And this is only the free version of the app. There's more, if you're willing to shell out some money for the Pro version (US$4.99 a month or $44.99 a year). Additional features include the ability to attach files, assign specific tasks to people you are sharing the list with and the ability to chat with people through the app to make sure all tasks are on track.
For an app with such a clean minimalist look, it does a pretty decent amount of stuff. If you need a little help getting organised, this could be the task manager you're looking for.