We all know that its great fun(and, sometimes(like all things in DF), great !!FUN!!) to chain a dragon at your main entrance and set a booze stockpile for massive loads of goblin and elven gibs.
I don't know if anyone has ever thought of that, but in the middle ages some people developed a way to defend themselves with nothing less than BURNING OIL to soak their enemies in a never-dowsing fire.
To quote
wikipedia:
The simplest, and most common, thermal projectiles were boiling water and hot sand, which could be poured over attacking personnel. Other anti-personnel weapons included the use of hot pitch, oil, resin, animal fat and other similar compounds.
How to implement that on DF, you ask?
First, add the reaction for creating burning oil at the kiln. Reaction would be a metal bucket and tallow(maybe pitch, if pitch ponds in swampy areas were added).
Then, the hard part. Acctually creating the fluid Burning Oil, which would sink into the ground the moment it is released(or maybe a vertical fire breath).
And, of course, the {b}uilding Burning Oil Support, which would require a block(in this case, to build the support) and the bucket of burning oil. That would be conected to mechanisms. Could also be used as a floor trap.
For added realism, oil could eventually cool(becoming tallow again), or maybe ever become useless in colder climates.
"What would be the use of that?"
-To allow military dwarves to shoot vertically.
-Because of the context. Massive forts with a wall defence of sorts
-Because its fun to see !!GOBLINS!! running aimlessly.
What do you guys think?