An elite fighting organization falling under the Department of the Navy but grabbing it's own representative on the Joint Chiefs of Staff. If a marine is confronted with this fact, they will merely shake their head and reluctantly admit it's true.
A Marine will be the first to tell you that the Corps is better than the Navy, Army, and Air Force.
(There is generally a lot of tension between the Army and Marines, but only because the Soldiers couldn't make it into this day's Corps)
Army, "You serve?"
Marine, "Yeah, Marines. You?"
Army, "Yeah, Army. I'm sorry."
Marine, "Don't worry about it, we've been fixing the Army's mistakes since 1775, we're used to it by now."