Tanks do have a limited defense against laser guided munitions, many of the latest tanks have the ability to fir a spray of fog from their smoke grenade launchers intended to disrupt the beam from a guidance laser.
Ugh, still trying to look up the article on defense lasers I read for verification, but I do remember it saying that lasers of this sort don't overheat the target for burn-through (article was discussing ballistic missile defense), so reflective coatings wouldn't be a defense. The laser actually...
How about B-25's 'skip-bombing' attacks in the PTO? I remember reading an interview with Japanese sailors after the war where they were wondering how we got our air launched torpedoes to jump out of the water before striking their ships.