"This is a stickup, see? Now turn over all your valuables and no one needs to get hurt." Back in 1928, a line like that would have been met with chattering teeth and shaking, raised arms. In 1929, however, Chicagoan inventor Sammy Schwarz would see it answered with "a stream of lead bullets in his face."
Schwarz's breast machine gun works like so: the wearer raises his hands, which are connected to a gun, mounted on his chest, by two strings. One controls the aim of the gun; one fires. We imagine — in a world where Schwarz's crazy device was actually made real — the final version of this machine gun vest would be concealed under regular clothing, with the strings running up the inside of one's sleeves. Of course, then a 1929 Chicagoan would have to decide what's a larger loss: the money in one's wallet or blasting a hole through one's fine suit.
Here's the full spot from Modern Mechanics (click to enlarge):
This irresponsible self defense wet dream first appeared in the May 1929 issue of Modern Mechanics magazine, and was spotted by io9's Cyriaque Lamar. Lamar's put together a fine list of odd armors from the early 20th century — take a look.