The Walther P5, Sig P6, and H&K P7 were also designed to allow safely dropping the slide on a loaded chamber. It was one of the requirements that they had to meet to be adopted as service pistols. I know the Beretta 92 series pistols allow this as well.
All these pistols have an extractor with a ramp on the outside surface of the extractor, forward of the hook, to allow it to slide over the rim of the casing more easily.
I don't personally see the purpose of doing this regularly, on any pistol, even if the pistol and extractor were designed to allow it, and if I lose the magazine and I need to load the pistol and fire it, I would load it and fire it regardless of whether or not the pistol and extractor were designed to allow it.