There are going to be guns, lots of guns. Some (pistols, rifles, swords, tasers) could plausibly be owned by just about anybody. Other weapons (sawed-off shotguns, rocket launchers) are rarely legal in most states. That said, a cello case could hide just about anything. Would our most merciful GM staff be willing to offer guidance on the in-universe legal/social implications of open and concealed carry by weapons class? I suspect that, at a minimum, this should have costuming implications.
Cheers,
Washington Irving (formerly Herbert Wayland Baker, concealed firearms misuser)