Ok, who's the other dude who voted for United v Liverpool?
For me it's the biggest football derby in the World. If both clubs had 150,000 seats every match would be a sell-out. The only other contender is the Old Firm, but that goes beyond sport.
In Rio, the main derby has always been Fluminense v Flamengo (They are the two most popular clubs in the city) or as the locals call it, the "FluFla" or is it FlaFlu?. :?
The Latin American derbies are probably be the most volatile, along with the Istanbul one; although two Cairo (Forgot their names) teams claim to have the biggest and meanest derby in the World.
Other notable derbies are:-
Ajax v Feyernoord
Schalke v B Dortmund
Bayern v B Dortmund (The two giants of the Bundesliga)
Arsenal v Tottenham
Bayern v TSP 1860 (Munich)
Corinthians v Sao Paolo
Sporting Lisbon v Benfica
Real Betis v Sevilla
Bohemians v Sparta Praha
Penarol v Nacional (Montivideo)
Newcastle v Sunderland
Real Madrid v Atletico Madrid
Lazio v AS Roma
Juventus v Torino
Sampdoria v Genoa
Independiente v Racing Club (Avellaneda, Buenos Aires)
Newells Old Boys v Rosario Central (Rosario)
Aston Villa v Birmingham
West Brom v Wolves
Burnley v Blackburn
Derby v Nottingham Forest