His post 9/11/2001 monologue

I only saw it once, back when it aired the first time, but his post 9/11 monologue was so moving, it gave me chills.
I enjoyed David Letterman a ton. He seemed like a very sharp, intelligent interviewer, while also indulging in zany humor and his odd banter with Paul Shafer. A lot of bands got exposure on his show, he just seemed to have a lot of influence.
So when he got serious about the motivations of these religious zealots, the mixture of anger and dismay was so evident, and he was so forceful and articulate, I think of it as one the greatest moments in television history, although precipitated by a truly horrific event.