Safe and perfect answer: The person behind the camera.
Honest answer: The camera
Look at what they have -
1. winners of photo competition
2. the masters
3. most people on forum who say it is the person behind camera
If you lend me a D90 with a 17-55mm f2.8 lens, I can do a better job than what I can do with my D40 + 18-55mm kit lens.