Task List - Personal task manager and to-do list app for iPhone and iPad
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Habitify - The easiest way to keep track of your habits
TaskPaper - Plain text to-do lists for Mac
Capsicum by Illuminated Bits - Plan your day. Track your habits. Tell your story.
Microsoft To-Do - Task management tool