Note the obvious sarcasm. 90% of magical modifiers on weapons modify THAT WEAPON, and that weapon alone.

Example: You have a weapon that deals poison damage, and a weapon that deals cold damage. Both are not applied to both weapons, your barbarian swings his weapons independently. Try it sometime, using a standard attack.

Exceptions are made when the effect does NOT have an offensive/defensive ability (like the +30 all stats from BOTD). Enchantments on jewelry and charms affect the WHOLE, not just itself. -.-