Useless artifacts in my current fort:
ushrir Idolcloister, a green glass trumpet
Weight: 10
Value: 30000
This is a green glass trumpet. All craftdwarfship is of the highest quality. It is encrusted with obsidian, decorated with green glass and saguaro rib wood and encircled with bands of obsidian. This object is adorned with hanging rings of obsidian and giant cave spider silk and menaces with spikes of copper. On the item is an image of shining suns in elephant leather.
That trumpet may be incredibly useless, but I wouldn't call it "worst" since it sounds pretty badass.
It is a pretty badass trumpet; and if I had a trumpet like that, I might actually go back to playing, but I don't think dwarves actually use instruments.
Anyway, to add to the list, some migrant child was possessed by something to use two platinum nuggets (plus other stuff) to make a mug. According to the wiki, dwarves use a measurement to weigh things similar to kilograms, so by my calculations, it is a 46lb mug.
Drinkkissed the Pregnancy of Citadels, a native platinum mug
Weight: 21
Basic Value: 169200
This is a native platinum mug. All craftdwarfship is of the highest quality. It is studded with brass, decorated with green glass and encircled with bands of giant cave spider silk, cow leather, green glass, copper and dog bone. This object menaces with spikes of native platinum. On the item is an image of a acacia in cassiterite. On the item is an image of a hide root in native platinum.
I don't even get a stone crafter; instead a useless child that will grow up into a skilless dwarf.