I am not sure where the glass making will go but it seems to fit here...
Hollow arrowheads. I would want to be able to make various types of arrowheads that could be filled with various things like poison or naphtha. Possibly make a blunt arrowhead that will burst when it strikes the enemy for the naphtha and a sharp one shatters and releases poison within the enemy.
I know people are probably wondering why i suggest the poison delivery like that when we can already coat the arrow with poison and get the same effect. What I suggest is that the poison delivered in this fashion would be more potent then the normal way. This is because there would be more poison within the arrowhead then there would be if it was coated in poison.
