There is unlikely to be one ultimate joke, jokes can be a variety of things.
But is there an ultimate quirky joke, or satirical joke, or rude joke? The Goons "What's the time?" "Eight o'clock, I have it written down on a piece of paper" may be a contender for ultimate quirky joke-certainly it's the ultimate in quirky dialogue-but does it stop being as funny through familiarity? And there can't be an ultimate topical joke.
What do you think?
NB, people can't be nominated as ultimate jokes...