Well, at a Federal Level, there was the case below. But it's a guy robbing a bank, not a guy defending his property, so obviously it's quite a different use of a fake or unloaded gun.

Arrest and trial of Lamont Julius McLaughlin

At approximately 9:30 a.m. on July 26, 1984 Lamont Julius McLaughlin and a companion entered a bank in Baltimore, Maryland wearing stocking masks and gloves.[7] McLaughlin "displayed a dark handgun" and ordered patrons to put their hands up.[7] McLaughlin's companion then jumped over the counter and placed approximately $3,400 in a brown paper bag.[7] When McLaughlin and his companion attempted to leave the bank, they were immediately apprehended by police.[7] Officers seized McLaughlin's gun, but discovered it was not loaded.[7] At trial, McLaughlin pleaded guilty to charges of bank robbery and bank larceny.[8] He was also found guilt of assault during a bank robbery “by the use of a dangerous weapon" based on the district court's determination that the unloaded gun was a "dangerous weapon" within the meaning of federal bank robbery statutes.[9] On appeal, the United States Court of Appeals for the Fourth Circuit affirmed McLaughlin's conviction.[8] McLaughlin appealed again to the Supreme Court of the United States, which granted certiorari on November 4, 1985.[10]

Opinion of the Court

Writing for a unanimous court, Justice John Paul Stevens provided three reasons why an unloaded gun is a "dangerous weapon" under the federal bank robbery statute.[8] First, Justice Stevens argued that "the law reasonably may presume that such an article is always dangerous even though it may not be armed at a particular time or place."[8] Second, he argued that "the display of a gun instills fear in the average citizen," even if it is not loaded, and "creates an immediate danger that a violent response will ensue."[11] Third, he argued that an unloaded gun "can cause harm when used as a bludgeon."[12]