I'm from New Jersey. "Biscuits" are biscuits.
Examples of Usage
In the Outkast song "Red Velvet," from their 2000 album Stankonia, rapper Big Boi very clearly refers to his gun as a biscuit. He warns his opponents that, while they might have bodyguards, he lets his ... n-word "tote the biscuit." He goes on to explain that the biscuit will get blood on your hat and leave you slumped in your Cadillac. A biscuit can kill you, and the biscuit is obviously a gun.
You didn't need a picture of a gun to illustrate what a gun looks like, but here we are.
In the first verse of the Eminem and Dr. Dre hit "Guilty Conscience," Dre and Em play the good and evil halves of the conscience of a man who is considering robbing a liquor store. Eminem, irrepressible rogue that he is, encourages the man to rob, while Dre, always the voice of reason (he's a doctor), advises the man to "drop the biscuit," as "it's not worth it to risk it." The man agrees (thank goodness!), and abandons his scheme. Contextually speaking, it would be absurd to assume Dr. Dre was referring to an actual biscuit, or anything other than a gun.