Yes, that Gustav would be the weapon of choice, but it certainly isn't available to the general public. It would also be a heck of a lot of fun to shoot.
I'd also enjoy a full-auto weapon. Cripes, dad got to lug around a BAR in WW-II, the lucky guy. I don't think that he considered himself lucky at the time. Germans seemed to train their Mausers on the gun that went "rattattattatta..." rather than the ones that just went "bang".
Anyway, folks are destined to use the cards that they are dealt - which around these parts generally means handguns on the road and medium-bore rifles at home. It means we have a fighting chance against these types of thugs, but only if we can find them before they target us. And, if we can catch them in the act or sufficiently along in the act as to be easily construed in the court of law as a threat. Its better than nothing by a long shot, but certainly not as good as it could or should be.