Adamantine weapons (10 pieces of ammunition)
Normal hits against objects are critical hits.
+500 Gp cost.
(pg 78 Xanathars)
Adamantine armor
Critical hits against you are normal hits.
+500 Gp cost.
(pg 150 DMG)
Mithral armor
Does not impose disadvantage on stealth checks.
No strength requirement to wear.
+500 Gp cost
(pg 182 DMG)
Mithral weapons (10 pieces of ammunition)
Half normal weight.
+500 Gp cost.
(House rule)
Silvered weapons (10 pieces of ammunition)
More effective against certain enemies.
+100 Gp cost.
(pg 148 PHB)
Darkwood weapons (10 pieces of ammunition)
Half normal weight.
+500 Gp cost.
(House rule)
I wish you the best in all your violent endeavors.
–Argo