The Grease Gun.
Nothing says 'industrialized nation' more than a fully automatic firearm that can be produced for around $20 and in quantities that would make Ford's production line blush.
The M3 and later M3A1 'Grease Gun' is a superb weapon. Firing the 45ACP round at around 450 rounds per minute the Grease Gun was as distinguishable on the battlefield of the second world war as an AK-47 was in the jungles of Vietnam.
Simple, reliable, robust, and a blast to shoot!