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
CheckFlow.io - Simple process and workflow management software using powerful checklists. Create recurring checklists, workflows and standard operating procedures.
Microsoft To-Do - Task management tool
Nifty - Manage projects, work, and communications in one place.