(Rare): Person who strongly believes in the Policies of Communism, such as Lenin or Marx.
(Uncommon): Some bored, computer addicted Aryan who read a 2 paragraph definition of communism, and now wants the whole world to convert to it, by saying "Peace, justice, and freedom" on the internet. An example are Liberals or Democrats.
(Common): Some 13-25 year old dude who saw a video of a parade from the Soviet Union on youtube, and now goes to school wearing a Che Shirt. Such as Sam Webb or Andres.
Communists, Rare, Uncommon or common, are all a bunch of crazy Mo- Fos.