I was thinking, introducing lead as a new metal might bring about some new items ingame.
Lead Shot - Long before the use of lead shots as ammunition for firearms, small, mostly round lead balls were used for ammunition in slings. Perhaps giving a damage bonus to slings like arrows for bows.
Sap - Contrary to what movies show you, sapping someone with a hard, blunt object will concuss them more than knock them out. A traditional sap was a leather or cloth bag, roughly cylindrical, filled with small pebbles, or, in out case, the aforementioned lead shot. Sapping someone would knock them out similar to how I get roflstomped by a boar, having a success rate based on your stealth, maybe modified by the other person's constitution. Obviously a helmet would make this igh impossible without herculean amounts of strength (if possible at all)
Caltrop - pretty simple, a small cluster of three spikes arranged in such a manner as to always have one spike pointing upwards.
I know you could theoretically do these things with almost any other metal, but historically lead was used due to it being both heavy and malleable. At low temperatures (low relative to other metals/alloys) lead becomes very soft.
--EDIT--
Caltrops have 4 spikes. Counting fail on my part.