Giving your items a little flavor now and then can help to enrich the setting, make mundane objects seem appealing and interject some mystery into story ( "what is a Ninjato doing here all the way from the city of Lo'h"). You can apply these same "historical" arms, armor and equipment to races to help differentiate them from humans for instance. Movies like the Lord of the Rings did a great job of really identifying that the items ( weapons, armor, items, etc) used by elves was very different than those used by dwarves or the riders of Rohan.
Items can be used in a campaign/story to convey cultural/racial differences but also class/cast differences ( "That's a Knights Great Sword, what is a common adventurer/tomb robber doing walking around with a Knights Great Sword. Are you a Knight?" asks the local militia suspiciously). Also if your trying to set the tone of the Age you are playing in, then a crossbow for instance would not exist in the Bronze Age setting ( unless you wanted it to I guess). So items found in the adventure can also convey ancient history without necessarily having to be powerful magic items (" Wow, all these skeletons posses the ceremonial armor and obsidian edged war clubs used by the Jaguar Warriors of the Tekunakan. They were wiped out nearly 500 yrs ago, I believe we may have found an ancient Tekunakan burial site"). You can also use items like this to introduce lost technologies into your game ("You find a sword, but its not made of bronze like swords you know to be, it is made of a hard shiny silver metal and seems stronger (steel). Whom or what crafted this item is unknown but details of its manufacture is surely beyond anything you possess knowledge in").
Below are some great supplements that I have found very helpful in introducing this kind of flavor into my games:
Arms & Equipment by Troll Lord Games
Arms and Equipment Guide by Wizard of the Coast
(d20 rule mechanics, but plenty of good info and ideas for any game style)
"Historically Accurate" works put out by Osprey Publishing
Great collection of work by Palladium
2nd Edition AD&D Arms & Equipment Guide
From Stone to Steel by Monkeygod Enterprises
( contains rules in back for d20 style mechanics)
...And a 10- Foot Pole, a complete guide through the ages of arms and equipment and day to day items
Aurora's Whole Realms by TSR
A Sears catalog of goodies for your everyday adventurer