Damaged Weapons (3.5e Variant Rule)
From D&D Wiki
These are rules for weapons taking damage and being broken. Upon scoring a 1 (d20) with a melee weapon the weapon is chipped; there is no statistical penalty's from a weapon being chipped. If a chipped weapon is used and scores yet another 1 (d20), then the weapon is damaged, a damaged weapon takes a -1 penalty to attack rolls. If a damaged weapon is used and scores a 1 (d20) then it is broken. If the weapon is magic, it gains a special protection from being damaged, they have a 4 part breaking process instead of three, but if a magic weapon only suffers a single roll of 1 (d20) on any given day, that will self repair overnight, however if a magic weapon scores two 1's (d20) on that given day then the weapon is chipped and doesn't self repair, and continues to take damage as a normal weapon. A bow or cross-bow, that scores a 1 (d20) will have its string break, although they only have a one part breaking process they are by far the cheapest to repair, a replacement string for a bow or cross-bow of any size is only a silver piece, and requires a DC 15 use rope check to put on the weapon. Guns that score a 1 (d20) explode and are the same price to repair as a completely broken melee weapon.
To repair a chipped weapon is 1/10 of its base price; to repair a damaged weapon is 1/2 of its base price; to repair a broken weapon is its base price.