i bought mirror reflective tint for my back window a couple years ago so that super bright headlights people would get a taste of their own medicine, but decided against it because i didn't want to be a dick just because others were being thoughtless
it would have been pretty effective i think because i drive a hatchback with a very vertical back window
I've noticed that I am quicker to drop my high beams when I approach an 18-wheeler at night with chrome mud-flaps.