Stand By, Ready
I haven't been able to find any written rule that would stop a character from using 3 one handed weapons or a two handed weapon and a one handed weapon together. I think a dual gun bandito would even retain his ability to crit with 3 pistols.
Just my 2 cents
Here you go:
SHadows of Brimstone Rulebook p30 wrote:
Normally a Hero is only allowed to make a Ranged Attack with a single Ranged Weapon. However, a Hero that has two Single-Handed Ranged Weapons may fire both as a single Ranged Attack! This is called Dual Wielding.
It would be worded differently if it meant anything else.