The Mangachasers have some fun videos showing off some cool techniques and style. While I think Manga can get a bit formulaic/samey there is no doubt that it can look super cool and nice Manga creation is a joy to behold.
The MangaChasers Youtube Channel has plenty more where that came from, all worth every second.
There are some lovely vids and sketches by Mark Crilley on his channel as well:
While we are at it, here are a few more magarish vids: