Chez Kiki - Aux Deux Amis, 1 Rue D'Atlas, Bellville, Paris
I've been eating here since 2004 and this place serves the best couscous in Paris. Chose from beef, chicken or merguez (very tasty spicy sausage). It's a small spot and gets ram-jammed at launch times.
Not sure of the proper name of this place (if it's Chez Kiki or Aux Deux Amis) but it's stone's throw from Belleville Metro and well worth schlepping east for.