The following are things I use regularly, but in a pinch, I can do without.
Check out these three:
Tokina 12mm - 24mm f/4.0 PRO DX Autofocus Zoom Lens for Nikon Digital SLR Cameras
Good, Sharp and worth evey penny...
Pros: Consistent Output, Durable, Sharp Focus, Strong Construction
Cons: Average Focus, Heavy
Best Uses: General Use, Night Photography, Landscape Photography, Special Effects, Macro
Describe Yourself: Semi-Professional
This is a good hearty lens that is as good or better as any DX WA lens out there. The only WA lens I have seen that beats it is the Nikon 14-24... of course that lens is the best available these days. The Nikon 12-24 is a fine lens, and some consider it better than the Tokina, but I honestly can't tell the difference.
Further, focus is not a real issue on WA lenses, this is not AF-S or its equivalent; but I can tell you I have never missed a shot because of the AF. The lens just doesn't have to travel far to focus... the nature of Wide Angle lenses.
It is sharp from corner to corner from f/5.6 on and there is only minor corner focus issues wide open. Very very sharp!
It can take filters very well, but don't expect it to take standard height filters if you want to go to the wide end. I have a thin line B+W CPL that I use with it that seems to do a great job.
There is a slight distortion at 12mm, but it is very minor and easily straightened in post processing.
It is really a fun lens with Macro tubes. Mostly at 18-24mm, this is a great and fun lens.
If you have the lower end cameras such as the D40, 60, 3000 and 5000, you will need to get the newer version with an internal motor.