On my car radio, KGNW puts significant splatter over 810 throughout metro Seattle. But I can tell it's there. Once I"m past Everett into points north, the splatter is less of a problem. KGO is a good example of the directionalized 50kw AM stations that I find are a good way to cover a large nighttime service area, with minimal fading. KGO can be heard reliably in much of Alaska during dark hours. Come to think of it, there are now fulltime stations on 800 or 820 in Portland, Seattle, and Juneau, so KGO is more of an "out of town" experience where it would otherwise have a strong nighttime signal.
From a technical standpoint (programming is another matter), stations such as KGO, WBZ Boston, KLAC Nashville (or whatever it's called now) and WWL New Orleans, and perhaps KFBK Sacramento and WKBW Buffalo are good examples of using the nighttime skywave on AM to reliably cover a defined area with a directional array. Any other examples come to mind that still allow for easy nighttime DXing outside a station's immediate "market"?