Robert De Niro humiliated Jay Z at Leonardo DiCaprio's birthday party according to the NY Post.  It seems Jay Z considers himself too cool to return phone calls. De Niro had been trying to get a hold of him about a song Jay Z was supposed to record for the Tribeca Film Festival. So when Jay Z walked over to say hi to De Niro, De Niro gave him the "you talking to me face".  

“Bob wasn’t in any mood to make polite conversation,” the spy says. “He told Jay that if somebody calls you six times, you call them back. It doesn’t matter who you are, that is just rude.” When Jay-Z tried to make a joke of it, saying he is terrible on the phone, a source says, “De Niro kept telling him that he thinks he’s the man, but that he was disrespectful.’ ” “Beyoncé came over, but that didn’t calm Bob down,” the source said, adding that afterward, “It was the talk of the party.

Oh I'm Jay Z I'm too cool to call Robert De Niro back. Settle down Hova. Just because you gave De Niro a shout out in your song "Empire State of Mind", it doesn't mean you are on his level yet skippy.  And for those of you unfamiliar with the "you talking to me" scene here it is, but warning he does have a few curse words in here.