While I have two weapons made of llama bone (a short sword and a spear, both devoid of description), my favourite is a bituminous coal statue: Egarfimshel, "The Old Persuader".
The item is a masterfully designed image of Gust Sprayedyear the human and a dwarf in bituminous coal. The dwarf is striking down Gust Sprayedyear. The artwork relates to the killing of the human Gust Sprayedyear by a dwarf in Riddledslings in The Axes of Gates in the midwinter of 85 during Etosp Spuspo, the Siege of Thorns.
It is studded with billon, decorated with cave spider silk and encircled with bands of bituminous coal, billon and cat leather. This object menaces with spikes of llama bone and pig tail fiber. On the item is an image of Stosbab Menacebowel the goblin in cow leather.
Ah, the good ol' persuader that is beating your enemy to a pulp. I like to think both figures are actually fully clothed with the silk and pig tail fiber. As for the goblin... well, he is shitting his pants. I guess.
This one has popped up a couple times in engravings... though it's an alder statue, Sneergrasped, that pops up an awful lot actually. Sadly, I had done it during one of my many extremely short reclaims of that fortress, and it didn't look remarkable in the slightest. Now, for the first time, I've not only survived my second goblin ambush, but I also managed to create what I consider a proper fortress. I should investigate what was up with it someday.
Special notice goes to a failed artifact in that same map. Long story short, I had twenty-something dwarves, they ran out of booze, and it was winter, so while they died of thirst, they also spiraled into madness and deadly tantrums. The sole survivor was a little girl who was barely old enough to walk around in the blood-soaked rooms and miasma. lo and behold, when all hope seems lost, migrants appear with their own little boy! So, they discover the small failure of a fortress with a sick, traumatized little girl, tons of miasma and flies, and way too much blood and body parts around. She dies shortly after their arrival.
What does the little boy do? He withdraws from society. But he can't find what he wants, so he starts drawing in the workshop.
What does he draw?
Skeletons.
(He didn't have time to properly fail his creative mood; I didn't have any animal I could butcher, and was a major failure at hunting because the buzzards had stolen everything during the first 5 minutes. Oh, and goblins happened, too. However, I can only imagine what went through his head when he arrived at Questbronze, and what the artifact would have looked like.)