#1 Edge
This feud has to go down in history as one of the best ever.
The two most important ingredients to make a feud memorable are: A great face and an equally great heel; and this feud had both, as the cunning and dastardly Edge proved to be the perfect foil for Mr. Good Guy John Cena.
Their epic rivalry started when Edge cashed in his Money in the Bank contract on Cena at New year's revolution PPV, just moments after Cena successfully defended his WWE Championship in a grueling Elimination Chamber match.
The rivalry between these two gave us some very memorable moments including Edge slapping Cena's father and Lita throwing John Cena's spinner belt so that Edge could debut the "Rater R" belt.
It is rumored that very few people backstage had the confidence in Edge to be the top heel, and it was, in fact, John Cena who wanted Edge to be his nemesis and gave a chance to Edge to prove his metal, thus becoming one of the best heels in the business.