Workflowy! It's approach of "one infinite tree" has been a very simple mental model for me (been using for more than a decade) and they're recently bumped it up

Workflowy! It's approach of "one infinite tree" has been a very simple mental model for me (been using for more than a decade) and they're recently bumped it up with some nice features like image support, optionally viewing lists as boards, and date support. They've had sharing and sync to Dropbox for backup for a while now (paid version). This is currently the only tool that works at "speed of thought" for me across a number of devices. Their hashtag support is the best I've experienced in any tool yet. For a sales pitch, the slack team apparently used workflowy to coordinate dev before they launched. https://workflowy.com https://workflowy.com