Prone Attack( Oriental Adventures, p. 65)
[Fighter Bonus Feat, General]
You attack from a prone position without penalty.
Lightning Reflexes (PH) , Base attack bonus +2, DEX 15,
You can make an attack from the prone position and suffer no penalty on your attack roll. If your attack roll is successful, you may regain your feet immediately as a free action.
Prone Attack is a bonus feat for fighters. It can be taken whenever a fighter is eligible for a bonus feat, as long as the character has met the prerequisites.