I'm like Scarface sniffin cocaine
Holding an M-16, see with the pen I'm extreme,

from Nas – N.Y. State of Mind Lyrics on Rap Genius

Meaning

There’s a famous scene at the end of the movie Scarface where Tony Montana stuffs his face in a mountain of cocaine and then comes running out of his office in a wild final attack with an M-16 (Scarface is regularly referenced in rap). Meaning he is as badass as Scarface:
http://www.youtube.com/watch?v=HJUt_x0gwug

In a later song with Alicia Keys recorded days after Uday and Qusay Hussein’s 2003 assassinations, Nas updated this line to:

I’m like Saddam Hussein
Still alive, staring at my dead childrens' burnt remains

To help improve the meaning of these lyrics, visit “N.Y. State of Mind” by Nas Lyrics and leave a comment on the lyrics box