One more vote for the 18-200 VRII. I used it often on my D200 and was always happy. I would just buy it and be happy.
I know you said just one lens, but... while you can always crop the picture to bring in details that were just a little too far off you are out of luck if you find yourself with your back to the wall and still not fitting the image into your frame. I would consider one of the excellent wide angle DX zooms out there. (My preference being the Tokina 11-16 F2.8) then you will be covered for 99% of the situations you may find yourself in.