The Rap Network Kanye West and Jay-Z, Dr. Dre and Snoop Dogg, Raekwon and Ghostface Killah, Lil Wayne and Drake: some rappers are best known for their  featured appearances and partnerships. After countless debates over the greatest rap duo of all time (still Raekwon and Ghostface, for the record), I was curious about how easily I could quantify the …