I have knowledge about an area of computing that very few people in the world know about, and very few people need to learn about it. Very rarely a questions gets asked, but when it does it's guaranteed the question may sit for months without an appropriate answer. When I joined SO in 2012 I went through all the unanswered questions on that topic and was able to give good answers to like 60% of them. Got a bunch of medals. But then never did it again.