Just about everyone who's seen Monty Python and the Holy Grail has at least one or two scenes that stick out for them. I'm no different (though I doubt this particular scene is the one that tops most people's list).
The Black Knight is funny, but after hearing it quoted approximately eight billion times, I've tired of it. The Knights Who Say Ni were never particularly funny. Castle Anthrax is a great bit, but not quite as great as this...