This suggestion covers 'Francisca Axes' which won't be called such in the game. I originally wanted to give this to Rohirrim Warriors due to their Anglo-saxon influence, but since Dunlendings already have axe-throwers and it would fit well with their barbaric styles.
The Francisca Axe would be crafted similair to a regular Throwing Axe, but on a Dunlending Crafting Table.
It would look like this:
It would deal slightly (.5 health) more damage than a regular Iron Throwing Axe, and once it hits an enemy or block, it has a 50% chance it bounces off, richocheting to a random direction. Every time it falls or hits an object, it should have a 10% decreased chance.
It also should deal melee damage equivelant to an iron axe.
I have three possible suggestions to add in the Francisca Axe.
a) A new Dunlending Unit is added called Dunlending Axeman (wether it replaces the axe-thrower or not is your choice), they wield Francisca Axes, and regular swords. Like Easterling Fire-throwers, they would throw their Francisca axe first, and then rush in with their swords. Only when they are out of combat and far enough from an enemy do they regain their throwing-ability.
b) Most Dunlending Warriors that do not wield spears or pikes have this throwing-axe as a one use weapon
b) Dunlending Axe-throwers use these Francisca Axes instead of regular Iron throwing axes.