I noticed some enemies, Forgotten Beasts or what have you, exude noxious gas. I assume the deeper you go one might find caverns full of or pockets of poisonous gas, fumes, dust or what have you as well. And even if that doesn't happen, I was thinking that it really doesn't matter how decked out with armor your dwarf is, if he walks into a noxious cloud that paralyzes his breathing, he's going to die. So what if, using small mechanisms and an animal stomach, bladder or some leather skins, the dwarves can make a gas mask or breathing apparatus to either filter out noxious gas or help them breath under water for a very brief period of time?
I imagine if that kind of air/liquid bladder container could be adapted to other things as well, combining it with a backpack and some kind of tubing or hose could make for a makeshift flamethrower -- possibly a seige engine flamethrower or other liquid or chemical sprayer could be possible too (igniteable fluid, creature venom, domesticated animal milk or ale for lulz).
And not to go all steampunk but if they can use tiny mechanisms to build a gasmask, how about some WWI style trenchcoats, goggles, and the like to protect their eyes in battle. Maybe some very basic gunpowder style musket-meets-crossbow weaponry. Stuff that's kind of effective but also prone to blowing up in dwarves faces?
Maybe that would lead to dwarf-on-dwarf warfare. Like other dwarven colonies or somesuch. I don't know. Fighting for territory sounds kind of cool but the mental image of dwarves now doing trenchwarfare just gave me a shiver.
I LOVE DWARF FORTRESS!!!!