The double agent is a great ingredient for a thriller, since they represent a high level of drama and intrigue. Like drama and intrigue? Then check out one or two of the six double agents, who were always looking out for numero uno.
Dr. Michaels, "Fantastic Voyage"
The lesson here: Be suspicious of Christians. The mission in "Fantastic Voyage" is to shrink down a crew of doctors to microscopic size and save the life of an attempted-assassinated diplomat. Spoiler alert: Donald Pleasance is a double agent who happens to be devoutly religious. Christian, fine, but Christian AND Donald Pleasance? Don't let him on the ship.
Slade, "The Mackintosh Man"
The plot of John Huston's spy thriller "The Mackintosh Man" starring Paul Newman can be charitably described as "labyrinthine." But there's a double agent in there, and Paul Newman is a spy sent to infiltrate a British prison in order to find more information on him. The action proceeds from there, and the double-agent played by Ian Brannen becomes one in a chain of spies and counterspies. And don't rule out Paul Newman, either: He has a pretty convincing British accent. Suspiciously convincing.
Seemingly everyone in David eXistenZ" is operating in some form of double agency. But let's talk about the assassin at the beginning, who uses a really creepy gun made out of flesh and bones in order to circumvent weapon scanners (it uses teeth for bullets, naturally). Most people wouldn't even want to touch that disgusting thing but this guy is so committed to his cause of assassinating a prominent game designer that he'll wrap his hands around it and squeeze the trigger. Gross.
Miranda Frost, "Die Another Day"
The James Bond films are full of double (and triple) agents, but here's one who is also a Bond girl to boot. Played by Rosamund Pike, she hops into bed with Pierce Brosnan's 007 under the pretense that they're both just working for Mi6, but it turns out the truth is much more insidious: She just really liked Brosnan in "Mars Attacks." Just kidding, she's working for the bad guy. She eventually gets killed by Halle Berry, which is the fate that awaits all who betray Pierce Brosnan.
Special Agent Rachel Wright, "I Spy"
Be wary of any and all attractive women in the world of espionage (keep your eye on the attractive men, too). That lesson was learned the hard way by Owen Wilson and Eddie Murphy in the practically forgotten spy movie "I Spy." This agent played by Famke Janssen turns out to be working for the bad guy, but she gets dispatched in a hilarious-but-still-cool way that is the movie's forte. We think.
Robert Hanssen, "Breach"
The real-life spy who was so good at what he did, they made a movie about him, Robert Hanssen was a CIA agent responsible for what many believe to be the greatest breach in security in American history. While working at the CIA, he was simultaneously giving secret documents to the Russians, using his ultra-Catholic personality as the perfect cover.