Hey now, don't go roping MDO into the same category! We all know MDO with a nice thick coat of lead paint still looks 90% as good as it did when you could still get lead in your paint.
Ayup, and one panel of fire resistant building grade acm is pushing $300, and you'll need to order 100 to even get 1. Ironically enough, gas station canopies are not considered occupiable structures, so they can be built with the super flammable versions of ACM, even though they are already covering flammable substances. Though I've never seen a gas station fire that wasn't going to melt the canopy anyway...
One thing I haven't seen mentioned here, as far as ultimate painted surface, is porcelainization. If you can find someone who still does it, they coat whatever materials in a layer of colored porcelain. Our tower letters have a coating of this, and when we recently pulled them down to rework the neon, the only 'bad' spots were where the neon shorted out and burned some porcelain off.