smokey
Honorary Master
They don't have one, but in the last couple of decades Arsenal have come close.
QPR iirc... recently though apart from Arsenal it has to be Barcelona. Buckets of bad blood there. Still, no rivalry can compare to the Liverpool/United one. Both teams have had very successful periods. Arsenal/Spuds come close, but not that much. Neither of them have been as successful as United or Liverpool.
EDIT: If either London team win the ECL at Wembley, I reckon that will kick off a huge rivalry.