You can follow through with a powerful melee attack.

Prerequisites: Strength 13, Power Attack.

Benefit: If you deal an opponent enough damage to make him drop (either by knocking him out due to massive damage or by reducing his hit points to less than 0), you get an immediate extra melee attack against another opponent adjacent to you. You can't take a 5-foot step before making this extra attack. The extra attack is with the same weapon and at the same bonus as the attack that dropped the previous opponent. You can use this ability once per round.