Timbaland
Timbaland is my favorite producer. Nas is my favorite rapper. I always thought there was untapped potential in their collaborations. Why? Timbaland's best work tends to lend itself to the darker, mysterious, and mystical which would compliment Nas's style especially the mystique. "You Won't See Me Tonight" is my favorite of their collaborations and "You Owe Me" is cool. I also thought Nas was dope on "To My" and "Hot Boyz" remix. Still, I think there was potential for something incredible, game changing even. I could even hear Nas killing Aaliyah's "We Need A Resolution" as a guest feature.
What I really wanted to hear out of a Nas/Timbaland track is the storytelling and introspection. Its not something MC's usually tapped Timbaland for, which would challenge him. Nas also flexes when he's on some atmospheric more R&B leaning production and I'm sure Nas could get Timbaland in that street bag as well given how Timbaland laced Banks' "I'm So Fly".
For an album, what would reallybbe crazy is Timbaland's knack for transitions and beat switches. Not saying it would have to be an albun of epic 7 minute songs, but 12-13 songs with transitions where one song seamlessly flowed into the next would be crazy. You might have one or two of those 7+ minute songs, but having most of them between the 2:30-5:00 minute mark would be dope.