You want a Nikon NC (Neutral Color) filter ....
What are you wanting to protect it from ?
A lens hood works well for general protection.
If you are going to get a filter, then I'd recommend buying a good quality one, otherwise it can degrade your image / cause issues
swiftflo said:I suppose you could say for general/overall protection.
Or a Hoya SHMC PRO-1 Digital Protector - http://www.jessops.com/online.store/products/71555/show.html?cm_vc=PPZ1