One of the traditionally-awkward aspects of the Dungeons & Dragons game system, going back to AD&D is weapon proficiency. Quite simply defined, proficiency with a given weapon means that a proficient character knows how to properly use the weapon in combat. Using a weapon one is not proficient with will incur certain penalties, most notably a penalty on all attack rolls. The problem has always been in determining which weapons a given character knows how to use.
In AD&D, this was accomplished by giving the various character classes a fixed number of starting weapon proficiencies (and in some most cases a restricted list of allowable weapons), with additional proficiencies being granted as the character progressed. The main problem with this was that the Fighter character, master of arms that he is, would end up with a stupendously long list of weapons he could use competently, but would run across an enchanted Ranseur and be at a loss as to how to use the darned thing until the following character level. In time, the Fighter would reach a peak point after which new proficiencies were of no practical use.
Third edition D&D addressed this problem by creating three major groupings of weapon types, “simple” weapons that nearly anybody would know how to use, “martial” weapons that only skilled armsmen would master, and “exotic” weapons, which were simply not typically in use, and required specialized training or exotic origin in order to put to good use. Fighters are considered to be proficient in all simple and martial weapons. Quite tidily done for any reasonably-standard D&D world.
But with third edition Dungeons & Dragons came the d20 system, the OGL, and eventually Privateer Press and their Iron Kingdoms setting. The Iron Kingdoms has a significantly different technology level than traditional fantasy roleplaying games, and distinct ethnicities with different cultures and martial traditions. How does the d20 system’s weapon proficiency match up? A quick search for threads regarding firearm proficiency rules on their forum will tell you that it works a little less well than you might expect.
I’ll be following this introductory article with some suggested lists of weapons that should be considered “Martial,” “Simple,” or “Exotic” based upon the Iron Kingdoms cultural groups. Expect most Khadoran subcultures to favor Axes, Cygnarans to favor swords, and so forth.