illuminati
A secret organization believed to exist by conspiracy theorists. They are portrayed as an antagonistic force who have manipulated many of the events throughout the world to achieve their own ends - particularly world domination.
The logo that is mostly associated with the Illuminati is the Eye of Providence - a triangle (mostly green or yellow) with an eye in middle of it.
The Illuminati also gained meme status after several people made "conspiracy therory jokes" with almost anything by trying to "decode the hidden message" that will usually end up with the number 3 or the word "illuminati" and is later associated with MLG meme compilation.