Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Taskade - Make lists, organize your thoughts, and be inspired to get things done. Taskade is a collaborative space for your tasks.
TaskPaper - Plain text to-do lists for Mac
Microsoft To-Do - Task management tool
Taskful - Deadlines, meet your match.
Slash - A "productivity machine" that forces you to do tasks 1-by-1