The funniest line I heard in a movie was in "A Private Function" with Michael Palin, Maggie Smith and Denholm Elliot.

DenHolm Elliot's character (stuck up doctor with delusions of high society) says to Maggie Smith:

"Madam, lunacy doesn't just run in your in your family it veritably gallops!"

It comes at the point where Maggie Smith character (wife of a podiatrist - Palin - and social butterfly wannabee) is playing piano and singing patriotic songs to cover the squeals of the illegal pig the butcher is killing.

God save the queen!

From DR. STRANGELOVE:

"Gentlemen, you can't fight in here...this is a war room!

I was going to upload a WAV clip of that Dr. Strangelove quote, but the system doesn't like that type of file, for some reason. Oh well.....

Not quite on subject, but I thought Bagdad Bob's briefings were the funniest thing I've seen in a long time. To have an Iraqui briefing while bombs were going off, the flip chart was rustling and the curtains were fluttering was priceless.