Wunderlist is a beautifully designed and simple to use to-do / task app you can use on multiple platforms including Android, iOS and Mac OSX. It is free for everyone, you can unlock additional features with a Pro-plan.
Pro Beautiful backgrounds
Wunderlist comes with 20 free wallpapers and 10 paid wallpapers for users to customize the background image in the Wunderlist app. In addition, advanced users can also use their own image as background image with few tweaks, which is absent in main Wunderlist app.
Pro Simple, useful task management features
Wunderlist features the standard ability to add tasks and organize them within lists, but one aspect in which it excels is the amount of detail you can add to each task. Rather than simple alerts, tasks incorporate a number of other options, including reminders, subtasks, notes, and recurring tasks. You can also star important tasks, which is simpler than the priority systems used in many other apps.
Pro Can add to your list via email or Google Now
If you're on the run or away from your device, you can add items to your list by email. You can also add notes to the list item using the body of the message. Wunderlist supports Google Now, meaning you can add to your list using native voice commands on Android.
Con Will be discontinued
Wunderlist was purchased by Microsoft in 2015, and will be discontinued after the release of Microsoft To-Do.
Con Acquired by Microsoft, So Future is Uncertain
Microsoft acquired Wunderlist in 2015, and therefore its future is uncertain. It's unlikely Wunderlist will continue to be an (1) independent product with (2) a free version and (3) continue to develop and innovate at a reasonable pace.
More likely, Microsoft will at least monetize Wunderlist the way it monetizes its other products. It's also likely that Microsoft will integrate it into its suite of office products and even its Windows operating systems.
To see what this is like search the Web for "Microsoft OneNote Mac OS X," and you will find a host of "standard" features only available in the Windows version, "official" documentation and tutorials that presume you have the Windows version (but never say so), etc.
One would also expect versions running on Linux to be worse or nonexistent. Also, Microsoft software in general tends to be bloated with marketable features but little concern for efficiency regarding memory usage, processing efficiency, or unobtrusive updates.