WASHINGTON -- A mystery munition knocked a U.S. Army M1A1 Abrams tank out of commission in Iraq, leading the Pentagon to question whether the terrorists have a secret weapon in their arsenal. An unclassified Army report says a projectile punched through the vehicle and drilled a pencil-sized hole through the hull. The hole was so small that, according to the author's report, "my little finger will not go into it." The Abrams tank is nearly invulnerable to attack. Only two have been disabled by enemy fire during the entire Iraq campaign, according to the Army Times. The other one was...