Daily Discussion: What are some of your favorite YouTube channels?

Late at night, before I go to bed, I often end up going down the YouTube rabbit hole, finding all kinds of weird and interesting things to watch. Generally, most of the YouTube channels that I watch on a regular basis have something to do with history, geography, science or geek culture. Some of my favorite channels are Cinemassacre, Variant Comics, Name Explain, and Today I Found Out, as well as the many PBS channels. What are some of your favorites?