Popularised by notorious conspiracy theorist David Icke, the 'Reptilians' cover up story is the quintessential nut job theory. The idea is that the world is secretly being run by shape-shifting reptilian aliens, who are manipulating just about everything from behind the scenes. Key reptilians include Queen Elizabeth II and Barack Obama, who are both allegedly blood-drinking humanoids from the Alpha Dragonis system.
Many sceptics have argued that the theory is pretty much stolen from the original V television series, in which aliens arrive on earth and also pretend to be human. The craziest thing about this theory is just how popular it is though. David Icke has supporters of his theory in almost 50 different countries, and his lectures often draw large crowds.
Worst of all, a Public Policy Polling survey found that 4% of registered voters in the United States believed in David Icke's theory. Good to see such sensible people in charge of who becomes the most powerful person (or lizard?) in the world.
Have you heard of any conspiracy theories that deserve to feature on this list? Do you think there's truth behind any of the ones listed here? Let us know below!