The Mother Fucking U.S. Marines.

When shit hits the fan on a legendary scale, there is one group of trained combatants the United States turns to. The Marines.

And you thought Chuck Norris was a bad ass.

1. The United States Marine Corps was established on November 10th 1775 by an act of the Continental Congress. A year later, the British got fucked up hard and America was formed. Coincidence? No fucking way.
2. The Marine Core is a branch of the U.S. armed forces, that fights in the air, on land, and sea.
3. The Deadliest weapon in the world is a Marine and his or her Rifle.
4. The rest of the world refers to them as "Those guys that will really fuck us up if they invade."
5. A Marine is expertly trained in hand to hand combat, survival, and can shoot the wings off a fly from long range while having sex with your wife.
6. Marines are often the first to respond to major events in the world, and are often on the front line in a war.
7. Marines don't die, they just go to hell and regroup.
8. They kick so much ass it's fucking ridiculous.

Boot Camp
In boot camp, you're dealing with the kind of shit that causes prison riots. Boot Camp consists of, but not limited to: sleep deprivation, intensive physical training, Drill Instructor, Drill Instructor, and Drill Instructor. Words can't describe the hell of Boot Camp, nothing can prepare you for it. It is a complete overhaul of your civilian life. You're being turned in to fucking Rambo. You're going to run laps until you puke from exhaustion, and you're going to keep running, not even stopping to vomit. In 13 weeks, the Drill Instructor would make sure you're up to the High Standard of the USMC, they mold you from a raw recruit into a U.S. Marine.

MCMAP

The average marine has been in at least two combat engagements per year since 1775. The Marine Corps close combat program has been incorporating techniques from the various countries they've killed people in, creating the "Marine Corps Martial Arts Program," or "MCMAP." MCMAP was formed in 2001, the modern program also teaches the use of improvised weapons and parts of the gun other than the bullets. MCMAP moves have the option to completely destroy whatever body part you have in your hands, just put it in excruciating pain, or kill the shit out of somebody.

Devil Dog
Marine lore offers a detailed story behind the nickname:

During the battle of Belleau Wood in France in 1918, United States Marines were ordered to capture a hill that was heavily occupied by German ground forces. As the Marines made ready to charge the hill, word came down that the Germans were preparing to use mustard gas to repel the attack. As a precaution the Marines wore gas masks, which at the time had a prolonged shape that somewhat resembled a snout. While the Marines fought their way up the hill, the heat caused them to sweat, foam at the mouth, and turned their eyes bloodshot. At some points the hill was so steep, the Marines to had to scramble on all fours to climb up. From the Germans vantage point, they witnessed a pack of tenacious figures whose lower faces were obscured by gas masks but left open their bloodshot eyes and mouth foam seeping from the sides, advancing up the hill, sometimes on all fours, and killing everything in their path with the wrath of hell. As the legend goes, the Germans began to make claims to their superiors that they were being attacked by "teufel hunden" or "Dogs from hell."

Pretend for a moment that you're having sex with Jessica Alba and Anne Hathaway, while simultaneously killing a lion with your bare hands. You would still not be as manly or bad ass as a Marine.