Todoist. Why? Because it supports sub tasks and sub projects (this is pretty rare), freeform tagging so I control how I structure things, a wonderful UI and w

Todoist. Why? Because it supports sub tasks and sub projects (this is pretty rare), freeform tagging so I control how I structure things, a wonderful UI and works offline by way of HTML5 storage. I don't like that I can't hide tasks until they're nearing their due date however.