"My personal favorites are from Monty Python and the Holy Grail, but I'm not sure that film had enough "mass appeal" to make the list. "
I agree with your sentiment, but this is a list for the American Film Institute, so a Monty Python movie might not qualify.
DUH!!!
Right, it's the AMERICAN Film Institute. I am red-faced.
Oh well, any number of lines from "Airplane" would be an excellent choice.
PS I remember reading that Led Zeppelin, Pink Floyd and Jethro Tull financed the Python film. Who knows?