It's impossible to overstate how god damn cool Henry Gibson is. I was first introduced to him...well, I first perked up and said "who the hell is this guy" when I saw Magnolia, in which he takes a pretty interesting role and just spins gold with it. When I was writing my piece about the scores of Paul Thomas Anderson's films, I ended up watching a lot of his scenes over again, and that guy never ceases to be the most captivating, infuriating (jn a good way) aspect of that scene, this weird little character on the edge of the film who, in so many ways, makes the film. Really. Much like Ricky Jay's narration at the beginning and end, Magnolia would not be Magnolia without Henry Gibson.
That's to say nothing of the fact that he played, and wrote all the songs for the role of, Haven Hamilton in Nashville, which is...look, all the main players in Nashville are great characters, but the fact that basically his last line in the whole movie can put the character in a totally different perspective is astounding. That's good writing, sure, but if Gibson didn't sell it, we'd be left with a guy who's a self-centered ass, nothing more. Instead...just see the movie if you haven't already, it's amazing.
Oh, and he was the head Nazi in The Blues Brothers (which is really the first time I saw him), so, y'know...win.
He was 73. A much larger overview of his life can be found here.