The following was made for Into the Odd but you could apply it to any kind of dungeon game. Roll for the weapon type, and then for the description.
1 Sling (d4)
2 Dagger (d4)
3 Spear (d6)
4 Staff (d6)
5 Mace (d6)
6 Bow (d6)
7 Short Sword (d6)
8 Hand Axe (d6)
9 Longsword (d8)
10 Battle Axe (d8)
11 Longbow (d8)
12 Polearm (d8)
The weapon has some kind of inscription on it. It could be meaningful, or total nonsense.
The weapon is for training purposes and is not meant to be lethal. The damage becomes d4 regardless of what kind of weapon it is.
The weapon appears to be crafted in a rush or by primitive methods. While it works just fine, it looks like a piece of junk.
The weapon is scary looking, or has some kind of creepy decoration. You will spook commoners carrying something like this around.
The weapon is a hand-me-down, was scavenged, or is otherwise very old and battered and it shows.
The weapon came from another place, and looks kind of weird.
The weapon is elaborately decorated. Worth double the asking price, but makes you a target of pick-pockets.
The weapon is from another age, dug out of the ground of pilfered from ruins. Is of great interested to historians and collectors.
The weapon was crafted for a humongous person. Damage is considered to be die step higher, but only if you have 12 or more STR. Otherwise, all attacks are impaired.
Nothing special about this weapon at all.