To clarify. A 360 quickscope is when you do the jump, raise your scope, then shoot. A "no scope" is when you use a gun that would normally require you to scope, but you don't scope.
MLG is Major League Gaming, and is a real organization.
YOLO is You Only Live Once. While the mantra is intended to encourage one to make adventurous choices, which generally is a good strategy in life, it often is used as a joke to either self-observe or deride stupid decisions.
Swag is short for swagger.
420 blaze it is as above. 420 is supposedly the time of day that a group of high school marijuana enthusiasts would gather by a statue of Louis Pasteur to look for a patch of cannabis that was supposedly growing nearby. Here's an article that a quick Google search brought up: http://www.laweekly.com/news/mythbusting-420-its-one-true-origin-and-a-whole-lot-of-false-ones-4177495
Illuminati Confirmed is a parody of conspiracy theories regarding finding evidence of a conspiracy out in the open. Consider, for instance, that there are real Masonic symbols on American money, such as the Eye of the Architect. The Masons are a real fraternal organization that many of the American founders and subsequent leaders were a member of. The world was a different place, and such social clubs were a better way to spend your time than playing Call of Duty. Regardless, whether the Freemasons had more to do with American history than simply embedding a few of their symbols indelibly into our country's symbolism is debatable, but the presence of their symbols is not.
Another organization, one that was a bit more insidious, was the Bavarian Illuminati. They used similar symbols http://en.wikipedia.org/wiki/Illuminati Regardless, the Illuminati were banned. There's some backing to the idea that they merged with the Masons, but I'm not a Mason and have never invested that much interest into the matter. There are some theories that say that they wanted to overthrow the government, or kill off the population because agricultural technology wasn't sufficiently advanced to feed the population, and they didn't want to starve to death. These latter theories are, as far as I know, simply conspiracy theories, or justifications for their illegalization.
Regardless, "Illuminati confirmed" refers to finding their symbols somewhere, and therefor finding evidence of a conspiracy that they are a part of. On websites and television, content producers would often highlight the Eye of the Architect, to show the presence of Masonic involvement. This is found on the back of the American dollar bill, and if I understand correctly, a representation of the Christian God. It's an eye in a pyramid. This has recently devolved to simply drawing triangles on things to make a joke regarding evidence for a conspiracy. Since people actually know Masons, the Illuminati offers a somewhat more shadowy organization to blame, since you'll never find a member of the Illuminati to ask about the matter.