The following is a list of the most common weapons one is likely to encounter in a campaign (and some, like the heavy machine gun and anti-materiel rifle) that will probably not be seen in most campaigns, but are given to grant a sense of scale. If the GM or a player wants a gun not on this list, then the best place to start is by modifying an existing weapon. Firearms come in all shapes and sizes, with hundreds of manufacturers and tens of thousands of different types and models, so it is a safe bet that nearly anything that can be designed with these rules (within reason, good luck finding a gatling 10 ga. shotgun) is available on the market somewhere.