The AH-1 Cobra is a light assault helicopter.
It can be called in during Survival games, costing $20,000 after being unlocked for 10 Shards.
One person can only have two active Helicopters (Cobras or Apaches) at a time.
Cobras are armed with a machine gun, they seek out and attack enemies on the map. They are not as durable/powerful as Apaches, so it is recommended to buy Apaches instead unless you're saving money.
In later waves during Militia Survival or Chaos Survival, Cobras and Apaches can both die very quickly to powerful militia weapons.