Apparently you don't understand museum exhibits. What you see there is the one example that the museum has in its possession. The few exceptions are prototypes that were superseded by improved models and custom-built one-of-a-kinds (e.g. the sarcophagus of Pharoah So-and-so) and Art museums. (There is, after all, ONE Mona Lisa.) For example, http://media2.s-nbcnews.com/j/MSNBC/Components/Photo/_new/1000721-Florida_Muscle%20City-hmed.grid-4x2.jpg every car you see there are different from all the others. But NONE of those cars are truly unique. Each is just one example of that particular make and model of that particular year.
Exhibits of historical significance are not so much unique for what they are, but rather that they are the ONE that was used by a famous person and/or used for a historical event. Owner customization by the owner can make an item unique, e.g. King Arthur's sword, Excaliber (if it should ever be found to prove that it actually exists).
But when it comes right down to it, just how unique are weapons and armor, one from another? http://www.dreamstime.com/royalty-free-stock-images-collection-swords-sabers-image25961129 "Form follows function" and that applies to most weapons and armor. A sword consists of pommel, hilt, quillons, and blade. You can spice it up by encrusting jewels or adding engravings, but in the end the way they work is to "stick the pointy end in the other guy." With firearms, you can get a decent amount of variety: Anything from http://thehouseontherock.com/p7hg_img_1/fullsize/Guns_on_wall_fs.jpg to http://www.123rf.com/stock-photo/assault_rifle.html The more modern the weaponry, the fewer differences. Also, the less likely it is to find any one-of-a-kind weapons.
But in the end, what you believe would be interesting to see on display, and what others might like to see undoubtedly differ. "To each his own." "Different strokes for different folks." "Vive la difference!"