The Bell AH-1 Cobra is a specialized ground-attack helicopter. The Huey was made to carry cargo and troops, the Cobra was made to kill people. The Cobra has a faster firing rate and rockets, but costs more "merit" to call in than a normal Huey. The Cobra is highly efficient for killing some VC troops and can also posses a large danger to enemies positioned inside the base. This helicopter is best used against a massive VC attack or to soften the enemy inside the base.
The Huey Cobra was the first ever helicopter made for the ground attack role. It was used by the U.S. Marines and the U.S. Navy as the Sea Cobra.