Rokinon FE8M-N 8mm F3.5 Fisheye Lens for Nikon
The 8mm gets you an ultra wide perspective and that distorted look that fisheyes are known for. The trade-off is that the lens isn't quite as fast, but it is still an excellent option and sits at a nice price. Rokinon has included special programming so that this lens is compatible with autofocus (depending on the camera model) and features like focus confirmation. But, if you plan to use manual focus anyways, you can save about $20 by getting that option without the chip. This lens has a hood built in, as well as special coatings to cut back on glare and ghosting. The minimum focusing distance is a foot, which isn't bad, but there are better macro fisheye options out there.