Ken Brennan is a motorcycle-riding, iron-pumping private investigator who used his ingenuity and dogged determination to bring a violent criminal to justice. Sound familiar? That's because for years, filmmakers and writers have been conjuring fictional detectives with memorable traits not unlike Brennan's. Only time will tell whether Brennan himself catches Hollywood's attention. But in the meantime, here's a look back at some of the most famous pop culture private eyes and police detectives.