I use PlastX Clear Plastic Cleaner & Polish and it is amazing stuff. It will never cause a haze effect, and even if something is pretty clear looking already, give it a coat of this and buff off and it will feel smoother than glass. I polish each of my Sega Saturn/CD cases with it and I've always had impressive results. I won't claim that it can take deep scratched out, but I guess not much will if it's really deep.