In The Shadow of the Dead Gods
Metal is so scarce on Athas that most armaments are made of bone, wood, or stone. These substances are weaker than metal and fracture more easily. A broken weapon is at best an improvised weapon. Damaged magic weapons loose their enhancements, properties, and powers until repaired. The following option simulates the relative fragility of nonmetal weapons, making combat more unpredictable and exciting.
Reckless Breakage: When you roll a natural 1 on an attack roll, your weapon has a chance to break. You can accept the result, automatically missing the attack as usual, but keeping your weapon intact. Alternatively, you can reroll. Regardless of the reroll result, a nonmetal weapon breaks once the attack is complete. A metal weapon breaks only if you roll a natural 5 or lower on the reroll. This rule gives you a say in whether a weapon breaks. You can play it safe and except the errant attack, or you can attempt to avoid a miss by risking your weapon.