I'll second the wirehair, at least of the hunting breeds. I've owned them for over three decades and they were not to be trifled with when they got their dander up. My most protective one was a small female but the males were more impressive looking.
I've seen news footage of GWPs being used for crowd control in West Germany (it's been a few years) in which the dogs bit demonstrators. It wasn't a "grip and shake" like shepards but it caused an immediate reaction.
Based on what I have read of canines, it seems dogs in the 75-90 pound range fair best in the "wild" which I suspect they would be somewhat exposed too. Much larger and they have greater difficulty foraging their own food, health/physical issues crop up, and longevity decreases. Picking a dog in this size range would be my first decision with health being next. I would not be wanting an apprehension type dog so projecting force is not something I need. Many dogs will show a degree of protection towards their owners and with encouragement that can be enhanced to the point of the dog being at least a distraction/disincentive toward an assault.
To keep burglars, Jehova's Witnesses, and political activists from the door- a dog with a deep bark seems to work fine. If they jump madly against the door, that helps too. Noise is what they all dislike and the more of it, the faster they leave. Too, many "quiet" houses out there to choose from, no need for thieves to make a ruckus.
