Æther (3.5e Feat)
From D&D Wiki
Benefit: Once a day, before you declare an attack, you can use this skill to do an extra 2d6 damage on your next melee attack. If that attack misses, it provokes an attack of opportunity.
Special: If you use this on a foe wearing heavy armor, their AC is reduced by 5 for this attack. A character may gain this feat up to four times. Each additional time, you gain one additional use per day.