I really wish RethinkDB the company with all founders and engineers would have survived. Their documentation, polish, and web admin interface was heads and shoulders above.
The concept of changefeeds at the database level was super powerful. ReQL was nice to work with and using a ORM such as thinky[1] was a pleasure.
If only (I know it's not easy) they could have inked some enterprise deals and focused on the business and generating revenue.