Year: 2006 - Present

It's no secret that Lil Wayne and Jay-Z have always had a complicated relationship. The two MCs got along OK at first, but as more and more Wayne fans wanted to aware him the coveted Best Rapper Alive title, the relationship began to sour. Wayne's critical acclaim encouraged him to fire some shots at Jay, in interviews like this one and on wax: "You old-ass rappers better stay on tour/You're like 44, I got a 44, I'm 24/I could murk you and come home when I'm 44"). Of course the mere suggestion of any youngster taking Jay's spot was enough to make Jay fire back—although they've both appeared on each other's albums. This cycle of respect and dissing has been going on for years now, and like the ongoing battle between young and old MC's, it may never end.