The Enemies of Reason purely because I burst out laughing whenever you see it.
Richard Dawkins is sitting down listening to some New-Agers being all New-Agey. The look on his face is priceless.
In fact if you watch his face at about 23 seconds or so into it, you can see the exact moment he loses faith in humanity.
http://www.youtube.com/watch?v=gyQ57X3YhH4>>15814798? this opening