Tinfoil Hatter

Tinfoil Hatter is a normally derogatory nickname for a conspiracy theory buff, as the stereotypical image of one usually includes a tinfoil hat worn on the head to block out the mind control waves or chemtrails.

Did you hear that Ryan got coded at school for wearing a tinfoil hat around class?
Dang, I knew he was paranoid, but not that much of a tinfoil hatter!