I put some thought into what would be considered the 'classic' pulp weapons thismorning and I got what I thought would be a working list, any additions or comments welcome.
Pistol- Broomhandle mauser wins with the artillery luger in second place.
SMG- Thompson 1928 with a drum mag and a bergmann second.
Rifle- difficult to say, theres not much between bolt action rifles maybe mauser by default.
LMG- Lewis gun then MG08/15
MMG- I could only come up with a maxim I don't think others like the Colt potato digger or hotchkiss quite suit the role.
Stu
Pistol: For dashing English gentlemen: Webley
For your all American hero: Colt .45
For your White Russian or Commissar the M1895 Nagant
For bad guys, it must be the Luger
SMG: Thompson or MP18/MP28 or Bergmann (which dates from 1932)
Rifle: The Mauser really was the AK47 of the 20's and 30's - many countries adopted it or manufactured it under license: even the Springfield was based on the Mauser. So Mauser it must be, closely followed by the Enfield and Mosin Nagant.
LMG: I can't really see the MG08/15 being that popular when the Lewis and Browning BAR are available.
MMG: Any of the contemporaries really - depends on the setting so Browning M1919 for US based/backed adventures, Vickers for British, MG08 for Germans, Hotchkiss for French and the Maxim for Russian.
Shotguns: For your English gent or German count it really has to be a double barreled Purdey or similar, for the rest of the world the Winchester Model 1887/1901 lever action or Winchester Model 1897 pump shotgun. Bad guys could also opt for a saw-off.