Many years ago while holding short of 1R at Dulles, ATC told everyone to stop and hold position. The weather was awful and we were planning a 600 RVR takeoff. We were perpendicular to the runway (on the taxiway) for what seemed like an eternity while we waited for a clearance. All of a sudden we saw a green and white nav light pass from left to right. Cherokee got caught out there low on fuel (instrument rated apparently) and decided to fly the ILS (AT DULLES!) down to the ground without talking to anybody. Apparently he just picked up the localizer and came right on in.

In the OP, it's great that the controller eschewed liability concerns and stepped in. That's not always the case. About 15 years ago I was flying north of Detroit listening to a non-instrument rated pilot trying to get back into DET. The weather was two miles. The pilot kept asking to land DET and the controller kept denying him stating, "sir the field is IFR, say intentions." This went back and forth for 15 minutes before some random pilot on the frequency yelled out, "request a special VFR." The pilot did so and the controller immediately approved it. The controller was obviously playing by the book but this could have ended badly.