Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
nodo - Manage your daily tasks in the command line
Any.DO - The #1 task management app used by over 11 million people globally, Any.do is your free mobile and online task manager for Android, iPhone, Web and more.
TaskPaper - Plain text to-do lists for Mac
Microsoft To-Do - Task management tool
Proud for Mac - Break down tasks & boost your productivity