Coordinated Shot( Heroes of Battle, p. 96)
[Fighter Bonus Feat, General]
You are extraordinarily talented at making ranged attacks past your allies
When making a ranged attack against a foe who has cover due to the position of your ally or allies, your ranged attacks ignore the Armor Class bonus granted to the target because of that cover. Cover from other sources is unaffected.
A fighter can select Coordinated Shot as one of his fighter bonus feats (see page 38 of the Player's Handbook).