Here's a top-10 list (in no particular order) of private eyes that can be seen on the silver screen and on the boob tube...
1. Sam Spade of The Maltese Falcon: There are several screen versions of this character, but perhaps the best known iteration of Sam Spade was played by Humphrey Bogart. Spade is a noir-style detective that probably helped kick start the rise in popularity of the American detective novels during the pulp fiction era. He was a cynical character, but still was likeable enough for many fans to wish that Dashiell Hammett wrote more stories for the prototypical movie P.I. The mental image that some people imagine, a handsome man wearing a trench coat and smoking a cigarette, most likely originated from Humphrey Bogart's interpretation of Sam Spade.
2. Thomas Magnum of Magnum P.I.: The 1980's was the decade of television where the starring characters of the various hit dramas lived life in luxury and excess. It was no different for Magnum even though he was an investigator. He lived in a mansion, drove a Ferrari, chugged beers, was surrounded by attractive women that often were victims or were involved with his cases somehow, getting free rides in his buddy's helicopter, working only when he wanted to, and of course, living on the island of Hawaii. Magnum got to enjoy the rich lifestyle without being rich himself. In favor of his technical expertise, famous author Robin Masters let Magnum do anything he wanted. Higgins was the only thing standing in Magnum's way, but the two often found a way to co-exist.
3. The Angels in Charlie's Angels: Not a specific set of characters such as Magnum or Spade, the nickname "Angels" was bestowed on a group of women that work for Charles Townsend's private investigation firm. The first ones were graduates of the police academy that excelled in their training, but were relegated to lackluster roles because of their gender. Seeing the potential they had Charlie hired them and doled out assignments to the girls through Bosley. Every episode the girls would go undercover to solve a case, eventually being thanked by Charlie via speakerphone. The three key girls would often change out for others, but the moniker "Angels" never did change. Almost all the girls remained loyal to Charlie despite never meeting the man in person. That tradition continued even after the show jumped onto the big screen a couple of decades later.
4. Paul Drake of Perry Mason: The right-hand man to the most successful defense attorney in Los Angeles, Drake was the business suit wearing P.I. that would gather the necessary evidence that it would take for Perry Mason to eventually win his cases. He was sort of the stiff type, but managed to find himself dating nearly every single woman that made an appearance on the show...except for one. Della Street. He may not have been flashy like Magnum, but the results he produced were more than enough to prove that he was one of the most successful fictional P.I.'s around.
5. Sherlock Holmes: Guinness Book of World Records recognizes the character of Sherlock Holmes as the "most portrayed character in movie history". The private detective was usually aided by his physician buddy, Dr. Watson who was a genius at solving crimes on his own. With Holmes, the pair nearly solved every case that came their way from Scotland Yard. Sometimes more computer than man, Holmes would find clues that no one else would ever find, sometimes imparting his knowledge on how he solved the case to his best friend. Often depicted in the Victorian era, Sherlock Holmes was moved up into present-day London when he was played by Benedict Cumberbatch. Even in the fictional future, Holmes is a favorite of Data and La Forge in Star Trek: The Next Generation.
6. Hercule Poirot from Agatha Christie's writing: Holmes wasn't the only private detective in England that assisted Scotland Yard. Perhaps Agatha Christie's greatest character, Poirot was a refugee from Belgium who moved to England during World War I. During his time as a detective, he saved the British Prime Minister from abduction, undertook cases for both the British government and civilians alike, and traveled all over the world while sporting a mustache that could go head-to-head with Magnum's. Perhaps Poirot's most widely known case was Murder on the Orient Express in which he had to solve the murder of an American business tycoon on the famous train line.
7. Angel Investigations from Angel: A spinoff of Buffy the Vampire Slayer, the vampire with a soul fled Sunnydale, California to get over his broken heart after his breakup with Buffy. Unlike 99 percent of vampires out there, Angel was determined to "help the helpless" by starting his own private investigation firm that specialized in the supernatural. It didn't take long for him to form a team that would eventually take on the ultimate evil, Wolfram & Hart. Angel was the muscle and leader of the team, Wesley was the brains, Cordelia was the heart, Gunn was the street-smart muscle turned ultimate lawyer, and Fred was the science geek. Unlike the villains that Holmes and Poirot faced, Angel and his team would face vampires, demons, and even demigods on a nightly basis and not even blink.
8. Jessica Jones: A recently created Marvel comic book character, Jones was created in 2001 by Brian Michael Bendis and Michael Gaydos. She would go on to star in her own comic book series called Alias. The former high school classmate of Peter Parker (Spider-man) opened up her own private investigation business after her traumatic experience with Zebediah Killgrave. Under the mind control of Killgrave, Jones was depressed that no one knew she was missing for so long while he used her like a puppet. Her hatred for Killgrave was transferred from the comic book to the small screen via Netflix. The streaming service took a chance on Jessica Jones after Daredevil did well and now because of her popularity, Luke Cage (Jones' husband in the comic books) will also get his own series. She is the product of the streets, gritty, dark, and definitely not the positive role model type.
9. Batman: The Dark Knight is the only member of the Justice League that doesn't have super powers. He doesn't need them. He is perhaps the most prepared character in the comic book world and that's due to his investigative abilities. He was shunned for a while by the Justice League when it was revealed that Batman had dossiers on each superhero and knew how to kill each one in case they turned evil. At times, heroes were even surprised to find out that Batman knew their true identities. Batman's transition to television and the big screen was no different. Batman used the ultimate surveillance system, OMAC, to track the Joker down in The Dark Knight movie. Even as a teen in the current show Gotham, Bruce Wayne is using his intuitive skills to track down the evil-doers within Wayne Enterprises. And of course, there is the original Batman series that starred Adam West. That campy-version of Batman could solve any riddle left for him. His skills over the years have saved the world countless times.
10. Jessica Fletcher of Murder, She Wrote: A mystery writer and part-time amateur detective, Fletcher always found herself in the wrong place at the right time. Murder and crime seemed to follow her everywhere. A resident of a small community called Cabot Cove, Fletcher was a retired English teacher that always found herself involved in murder investigations going on in her hometown. The cops would often arrest the wrong suspect, but Fletcher wouldn't rest until she found the real one by utilizing her intuition and her ability to piece the clues together like others couldn't. If the fictional town of Cabot Cove existed in real life, it would top the FBI's crime statistic lists in homicides, but no one in Cabot Cove seemed to notice. There is even a theory out there that believes that Fletcher herself is secretly the killer in most of the episodes and is pining her crimes on others to avoid suspicion and boost her reputation for book sales. Either way, she is easily one of the best detectives on the small or big screen that doesn't have a super power.
Honorable Mentions: Shaft, Jim Rockford, Easy Rawlins, Dixon Hill (the fictional character within the fictional universe of Star Trek: The Next Generation that is played by Jean Luc Picard on the Enterprise holodeck), Tony Rome