Sword
Will makes the best swords in the islands, and perhaps further. That isn't idle boasting. They've been tested against most of the others.
His artistry lives in the blade, finely tempered and exquisitely finished. The hilt is so much frippery, especially the ones he makes for presentations and so forth, for show, for the men with more money than knowledge, who care more about the look of the thing than they do about its worth as a weapon.
His other customers don't make that mistake. These are the men who actually use the swords they buy, though only when there isn't time to reload or they've run out of ammunition. They tend to go for something weighty, not too long, and with only enough adornment to make for a good grip.
So when Will sets aside all his other responsibilities to make one particular sword, better believe that it will stand up to any test the owner puts it through. He takes almost excessive care over it, selecting the best materials from almost their earliest stages, beating out the blade with precision, fitting and fixing the tang as tight as can be... The hilt is gilt and set with a spiral of glass jewels: it looks gaudy, in a way that it wouldn't if the materials were real, and it takes a bit of knowledge to see how eminently practical the grip is. It definitely suits the intended owner.
Now all Jack has to do is come back for it.