Name your favorite productivity app and reason

Oh man, there was a post of a (new?/in preview?) productivity/project planning app on HN recently that I've been looking for in a while since I lost the link.

Hoping that shows up here again. I don't remember the name but the website left an impact. It looked really highly polished (a la Stripe).

Some of the features I remember:

- email integration

- tags and folder for organising projects

- richt text editing

Todoist -- being able to email in to projects/lists is a killer feature for me.