personally I'm enamored to my 35mm F1.8 AF-S. It's been the only lens on my camera for quite some time.
Beyond the classical virtues of a good lens: large aperture & sharpness, it has very fast auto focus. of course it comes with the expected fabulous color rendition and it's dirt-cheap too.
But the single most attractive part is the perspective. I love it for portraiture, street and even close-ups.
Additionally it's perfect for my "run-and-gun" portrait-studio: my bracket that takes both a flash and an umbrella. The amount of light from the 24" silver umbrella is perfectly ranged for a 35mm lens.
Although I don't have a Nikon version, I must share my enthusiasm for my 85mm F1.4 lens too - just like Palakaboy I find such a lens very useful. Mine is strictly manual focus, but very sharp and for $300, it's a hard bargain to say no to..lol.