What's the best Task Manager or To Do List (Software or Web)

Anyone find anything decent, it seems every product I come across has serious short-comings. This is what I want it to do, Manage projects > Tasks > Sub tasks. Tagging or assigning to multiple categories would be great for my modified GTD system. Free or non-subscription based would be ideal. “Task Coach” is pretty close but there are a couple of quarks that are annoying.

Update: I am using Windows