S.D.M.G.

The S.D.M.G is a straight upgrade to the Megashark, with the same fire rate and ammo usage bonus, except with a noticeably higher damage output.

It can be obtained by using the Extractinator, but it is a rare prospect.

Trivia

 * This item's description may be a reference to the indie title Edge of Space, in which rocket propelled sharks appear as an enemy.
 * This item could also be a reference to the book "The Hitchhiker's Guide to the Galaxy" in which all of the planet's dolphins flew off into space to avoid the iminent destruction of Earth.