To-Do Lists is one of those things that bugs me a lot. There are hundreds of apps out there but none of them seem to do them particularly well.

I think the perfect To-Do list would have

- the ability create (and allow others to create, subject to black/white-listing) a task by sending an email to my list

- the ability to delegate tasks to others (whether they're users of the app/service or not)

- order in a way that takes urgency, importance and deadlines into account

- an intray, so I can accept/reject tasks sent/delegated to me

- Mailbox app-style swiping to snooze tasks or mark them as Done

- shared To-Do lists (e.g. for teams)

- support for sharing tasks with others so they can comment on them

- API integration

- dependencies and workflows

I created some mock-ups a few months back to illustrate my thinking: http://jackgavigan.com/1tray-concept/