The lens that has least distortions, nevertheless, you could always PP the pictures to correct distortions

My vote will be a prime lens

anything at least 50mm onwards, or something that can control it like those perspective control / tilt shift lenses.
obviously if indoors, then ur going to run out of space with a 50mm...thats where those wider PC lenses help.

For architecture building, tilt shift is the best in the class for architecture shots. My suggestion is 11-16mm Tokina if you are on DX body. I have seen some commercial architecture shots done with DX body and the tokina lens. I have not try the 14-24mm before so I cant comment much on that lens.
Update : I have emailed about the TTA media pass. Still waiting for reply. Hoping for a respond on the next 5 working days

Lenses
12-24 mm DX zoom
14-24 mm full frame zoom
17-35 mm full frame zoom
14 mm full frame fixed
18-200 mm full frame
18 mm manual
70-200 mm full frame
80-200 mm full frame
80-400 mm full frame

Ah since you have the option to go for the 12-24mm (sorry for the typo earlier) Go for it. I managed to ask a couple of friends who have the lens and said that the distortion are well controlled for correction purpose and here is the link for you to judge it goodness

http://www.photozone.de/nikon--nikkor-aps-...-report--review