Which Nikon cameras are professional?

Which Nikon cameras are professional?

The answers by BrianR and Mrdat222 say it all. Pros indeed do tend to use cameras with physically large sensors, thus usually DSLRs.

The single-digit D-series and the 35mm F6.

Cameras are not professional, people are. The camera is just a tool.

Buying a "professional" camera won't make you a professional.