The subject of "ball lightning" comes up from time to time in the course of this research. It’s a fairly uncommon phenomenon, but is of interest here in part on the theory that, whatever it is, it somehow draws energy "from the vacuum" to sustain its output. New Scientist magazine recently published this article
that describes some efforts to create ball lightning in a laboratory. The article was brought to my attention by somebody over in the fusor.net group. You can follow their discussion of the subject here.