The most notable tool in the Men in Black's high-tech arsenal is not the Noisy Cricket or any deadly anti-alien weapon. No,it's the neuralyzer, the little vape-shaped device that lets agents erase and rewrite the memories of any civilians that arrive in contact with extraterrestrials. It's crucial because the Men in Black need to function in secrecy in order to be effective, and because,as a civilian myself, I really would not want to occupy any memory of most of these horrible aliens.
Source: blastr.com