Cobra is a Unique Sniper Rifle manufactured by Jakobs. It is only available in Mr. Torgue's Campaign of Carnage. It drops from "burner" enemies encountered in the Beatdown. It only has a .88% drop chance.
The weapon's "Red Text" is directly referencing that this rifle is making its reappearance from the first borderlands. Rounds fired from this Sniper Rifle, will be 100% chance of firing an explosive round.