I love anything visual. Used to Kibana, but now everyone is all over the graphDBs and stuff. Haven't even touched that, yet.
Would love to explore the relay landscape with heat maps or topic cluster maps, etc. We haven't really even started thinking of the real cool-beans stuff that can be done with an open dataset.
Nobody else has that because they try to make money off of controlling access to the data or forcing you to use their crappy API.