Not that I know of - but I stand to be corrected.
You've got nothing to ein, zwei, drei, vier
I'm only aware of the US having the trench gun, but I don't even think that was used in the ETO, something to do with the Geneva convention deeming it "inhumane" to be shot by it!
As far as im aware the US marines are the only ones in the world who use it because they kind of invented the combat shotgun during the american revoloution against british ships whils bording.
I think you'll find that the use of firearms which discharged a spread of pellets for naval purposes pre-dates the American revolution, they may not have been specifically called shotguns but that's what they were.
For example Blunderbuses, or even earlier something called murderers, although I think they were fired from a swivel mount.
Yes but i belive the US Marines used them alot more often in battle.