Weapon Manipulation (3.5e Feat)
From D&D Wiki
You may activate the special abilities of a weapon that you have Weapon Focus in as a free action.
As a swift action, while wielding a weapon that you have Weapon Specialization with, you may choose to suppress, restore, or transfer some or all of a weapon's special abilities in order to increase or decrease the weapon's enhancement bonuses. The transferred special abilities must remain as the same enchantment bonus power.
For example, you have a +1 flaming longsword. You could suppress the flaming ability to make the weapon act like a +2 longsword. Any changes that you make to the weapon last until you change the weapon again, or someone else wields the weapon.