I'm a big fan of Monty Python's. The first of their movies that I saw was "Monty Python and the Holy Grail". The odd humor really got to me and Monty Python is responsible for a lot of my most often used quotes of which you will still see quite a few, I'm afraid ;-)
The one I chose for today even became kind of a trademark for me at work for some time. Whenever numbers were our subject, I blurted this one out. I used it for my e-mail signature for a while, too. There came the time when it became annoying to have to explain it over and over again, though.
It's from the scene when the Knights around King Arthur have to deal with the killer rabbit guarding the cave they want to enter. Their only chance is to use a hand grenade, but first King Arthur has to be told how to handle it. "Then shalt thou count to three, no more, no less. Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, neither count thou two, excepting that thou then proceed to three. Five is right out."
I only use the part "Five is right out". Try it, you will confuse the heck out of people!