15. Ja Rule
Years on Def Jam: 1998-2005
Signature Def Jam Song: "Always on Time" (2001)
In the early 2000s, Ja found the sweet spot between R&B and rap and recorded a string of hits under the Def Jam moniker. But his ill-fated war with Curtis Jackson and a federal investigation of his label Murder Inc. upended his career as a 2Pac manque.