No Thompson SMG?
The very first SMG ever developed, to which all following SMGs owe their very existence? And ubiquitous to boot. 1.5 million were produced. Compare to the MP40 at 1.1 million produced.
No, I beg to differ. The Thompson deserves to be #1 on the list IMHO.
The first submachinegun was the MP-18 Bergmann. It saw service in WW1 and WW2.
The Thompson was manufactured until 1920.