A steel M1 military helmet once belonging to General George S. Patton is currently kept at Warehouse 13. It was a search result given by Artie's computer when he was attempting to find the reason behind the apparation of James. According to the computer, it has the power of mass telepathic communication. There is a warning "Do Not Wear!" along with the description. Presumably, the downside is equally impressive, if only the need to dominate those with whom one is in communication.
George Smith Patton, Jr. was a U.S. Army general during World War II that was best known for his leadership skills. It's probable that whoever wears the helmet can command groups of people telepathically.