Crystal ones will not (best options would be power support, or SGP). I think the majority of the other ones will at least a little. The only downside to crystal ones is that they are fingerprints and oil magnets.
I personally use power support anti-glares for my iphone. it takes away from the screen a little, but no fingerprints or oil spots. But if you are only interested in screen clarity, then Crystal protectors are the way to go.