Datomic and Datalog continue to amaze me, and give me hope that there might be a light at the end of the tunnel in terms of bringing us out of the depths of the SQL quagmire we've been stuck in for decades. Having the ability to persist, retrieve, and query data directly within the language you're using feel so much more natural than trying to mix in another language with a foreign paradigm into your applications (SQL) or sticking a contrived layer on top that tries (sometimes effectively, but with lots of edge cases and inside-baseball stuff to grok and deal with -- ORMs) to hide it away. I use SQL every day -- heck, to a certain degree even like SQL -- but this just feels... better.