Action 4 is among my most useful Gurps books. Its a great way to build characters quickly, either for NPC's who need more than the basic sketch, For one shot PC's that will be used only once, or for figuring out the capabilities of a tricky character. The Basic Action Template (BAT) (or another basic template) provides a starting point for the character, and then "Packages" are chosen to add capabilities.
One package in Action 4 is rather non-descript: Obsolete weapons. Rather than providing any real guidance, the template says to get enhanced parry, and then spend 12 points on skills and 8 points on techniques in the weapons you want. Flexible, but uninspiring.
Historical games are rather tangential to the main topic of action, but I find myself using the BAT and its associated packages for more and more. (see ICOPs, Gurps Action, and the BAT). The BAT can do more than just action, and It can do better than building "obsolete weapons" packages from scratch each time.
But there is a Gurps product that gives advice on building specific types of warriors: Martial Arts. Martial Arts has a list of 113-ish "styles", detailing how to buy skills and techniques to fight like almost any warrior in history. Using that as our guide, we can make more nuanced packages for the BAT.
We will rundown the classic melee weapon systems of history, with something of a European emphasis. We will cover: