I recently bought the Tokina ATX-116 Pro DXII lens. This is an 11-16mm f2.8 lens. I'm not usually very fond of third party lens but Nikon don't make a lens like this one and the closest one they do is way more expensive than the Tokina.
Despite the fact that this lens is in the reasonably priced lens bracket it feels like a pro lens. It has a metal mount and body. It is heavy and quite big. It is designed for DX sensors, at a pinch it can be used on an FX camera but you'll get vignetting at the edges if you go wide full frame.
It has a quiet built in motor so you can use it with cameras that don't have a built in auto focus motor. Focusing is fairly quick and because it's a constant f2.8 you get a good view and consistent exposure.
The zoom range is quite small but you can go for the 11-20mm version of this lens if you want more range. For me 11-16mm covered the range that I don't have covered already.
Even though this lens is very wide, any wider and you are starting to get into fisheye lens territory, it handles distortion and chromatic aberration well.
Below is a test shot of the side of a shed where you can see lots of horizontal lines. This shot is shrunk down for the web of course but the distortion and chromatic aberration are uncorrected. This is shot at 11mm, which is very wide.
We can see distortion of course but in my opinion for a shot at 11mm it's pretty good.
The lens comes with a sturdy lens hood which apparently will be needed because flare can be an issue with this lens, at a least in the DXI version. I haven't had chance to experience that issue yet but in this newer version of the lens (DXII) Tokina have made an effort to improve the problem.
Here's a shot I took today. This is the first snowfall we've had in London this winter. I took it fully zoomed out at 11mm.
I've found this lens to be sharp and I consider it to be what they say it is, a pro lens. Tokina don't make many lens and they seem to specialize in ultra wide angle lens. They are part of the same company that own Hoya and they use Hoya glass in their lenses, which I understand Nikon use also.
In conclusion I think that this is an excellent lens that fills a spot that Nikon haven't catered for. It feels solid and professional, looks good and does the job. On the downside it is big and heavy, but in my line of work that impresses people LOL.
Here's a link to the Tokina page for this lens: http://www.tokinalen.../atx116prodxii/