Sniping the Cockpit

No matter how badass your Cool Tank, Cool Plane, or Humongous Mecha may be, its crew is still often made up of flesh-and-blood human beings who, once you get past the vehicle's armor plating, are just as vulnerable to damage as any other. Enemies who have armor-piercing weaponry may come to realize that they can stop your rampaging murder machines with just a few well-placed rounds to the cockpit. In the same manner that a well-placed shot to the head can instantly kill a human being, an attack that deliberately targets and kills the pilot can stop a vehicle without having to exert the time, energy, and resources to reduce it to scrap metal.

This is common in newer First-Person Shooter games, where killing the pilot or other crew can take the vehicle or some of its weapons out of action until those stations can be manned again. Sometimes, especially if the vehicle itself has a Crew of One, it can also be used so that the opposing force can hijack the vehicle and turn it against its owners.

Disposable Pilot often overlaps with this.

Anime and Manga

 * Inverted in Gundam Seed: the Technical Pacifist Kira eventually trains himself to render any Humongous Mecha inoperable without any damage to the cockpit.
 * In an episode of Ghost in the Shell: Stand Alone Complex, a helicopter pilot suffers from a (deliberately induced) heart attack, which causes the AI in his aircraft to malfunction. This trope is invoked (since he apparently went into a coma) so it realises that he's dead and returns to base.
 * Standard operating procedure for the mecha in Bokurano.

Comic Books

 * The Saint Of Killers from Preacher pulls off several of these against a tank battalion. Of course, his magic guns (which were forged by Satan himself from the Angel of Death's sword) are guaranteed to never miss and always inflict fatal wounds no matter who or what they're aimed at, so really all he has to do is point, fire, and somehow someone is going to die. Whether it's by going through the tank's periscope, hitting and blowing up a round in the tank's gun, or simply by penetrating the armor, it's immaterial.

Film

 * In Return of the Jedi, this leads to the loss of the Super Star Destroyer Executor as a result of a Taking You with Me attack from a crippled Rebel starfighter. The massive ship was sent careening out of control and crashed into the Death Star.
 * In the World War I movie Flyboys many of the pilots are killed in their cockpits. In the final fight, the hero kills the German Ace with a well placed shot from a revolver while they are flying side by side.
 * Used in Avatar when the natives couldn't destroy the tiltrotors or Powered Armor wholesale, but could throw spears with sufficient heft to pierce the cockpits.

Literature

 * Shooting the pilots is noted to be an effective tactic against Ork flyers in the Ciaphas Cain novel The Last Ditch.
 * Tycho Celchu's trademark in the X Wing Series is doing this with full-sized starfighter guns.
 * In Harry Turtledove's Worldwar series, aliens invade in the middle of World War II. While the Lizards have technology and vehicles far superior to WWII era tanks and planes, they're still vulnerable to things like a tank commander getting his head blown off when he sticks his head out of the hatch.

Live-Action TV

 * In the 2000s version of Battlestar Galactica, Starbuck pulls off a variant of this against a Cylon raider she is dueling. Given the nature of the Raiders in this setting, however, this also overlaps with Boom! Headshot!.
 * Stargate SG-1: In "48 Hours", Teal'c takes down an al'kesh bomber by shooting the cockpit. With the gun from a Death Glider.

Tabletop Games

 * Common in the BattleTech universe. Since 'Mechs are difficult to produce in large numbers anymore, it's become common for pilots to attempt to kill one another with aimed attacks that try to minimize damage to the 'Mech itself.

Video Games

 * From the Command & Conquer series:
 * Command & Conquer: Generals has a hero unit that can snipe pilots out of vehicles, leaving behind the unoccupied vehicle that can then be captured by a friendly infantry grunt. The Chinese Nuke Cannon superweapon does the same thing, only on a larger scale.
 * Similarly, Natasha Volkova from Command & Conquer: Red Alert 3 is able to snipe the operator of a vehicle, at which point any infantry unit can hop in.
 * Can be done in the Mechwarrior games, which take place in the BattleTech universe (see above). Killing the pilot in Mechwarrior Living Legends also allows you to steal the mech - in previous Mechwarrior games, destroying the cockpit would simply "destroy" the mech.
 * However, in some previous titles, a clean kill would be more likely to allow you to salvage the mech after the battle, adding it to your arsenal in future missions.
 * At one point in Modern Warfare you do this to a Hind. Then Captain MacMillan does it to another Hind, which almost crashes on top of him.
 * Battlezone 1998 had a sniper rifle precisely to allow the player to do this.
 * Killing the pilot is one way to score a victory in Red Baron. As in Real Life, the open cockpits of many planes provide relatively little protection to the crew.
 * In Battlefield 2, the M95 sniper rifle and (occasionally) rockets are capable of bypassing the bulletproof cockpit glass of helicopters and jets, and killing the pilot.
 * This also works in Battlefield 3, as beautifully demonstrated in this vid. Most helicopters' windshields are bulletproof though, so it can only be done with sniper rifles or vehicle mounted machine guns. The Scout Helicopter's windshield is not bulletproof however, so you can just spray at it hoping to kill the pilot.
 * Tanks in World of Tanks have a crew that can be killed in battle. If the entire crew is dead, then the tank is effectively out of the fight, even if the tank itself is still in one piece.
 * The only way to take an enemy vehicle in Crysis is to kill its crew. A few well placed shots can net you an undamaged vehicle.
 * Silent Scope justifies this since the player only uses a sniper rifle. In one level you can take down a Harrier jet in one shot by scoring a headshot on either pilot - in another car chase level you can render everyone in a car ineffective by shooting the driver. This includes the boss, who attacks by trying to run you down with a hijacked semi.
 * In Mass Effect 3, Cerberus's giant Atlas mechs are somewhat vulnerable to this trope—while, as the codex entry suggests, their giant crystal canopies are less vulnerable than they ought to be, they can be broken. In singleplayer, Shepard can then Gundamjack the unit in question. (However, since its canopy has been shot out, he's now equally vulnerable...)

Web Comics

 * A Red sniper in Gone With the Blastwave does this to a moving plane. And causes the plane to crash into a crowd of enemy soldiers. However, it was done only as a stupid bet out of boredom.

Real Life

 * World War I, being the first major conflict to feature air-to-air conflict, notably had many instances of this. Before someone figured out how to mount a machine gun on a plane, pilots and observers were required to take firearms along with them in the cockpit in case an opportunity to attack an enemy craft presented itself. Generally, the plane's engines had usually more protection than the cockpit so often enough a plane would be shot up but still flyable but the pilot was dead or wounded. Manfred von Richthofen, the Red Baron, was fatally wounded by an anti-aircraft machine gun but still managed to land his relatively unharmed plane before dying.
 * During the Spanish Civil War, partisan snipers learned to shoot down low-flying fighter planes by targeting the cockpit.
 * This has gotten more difficult as technology has advanced, but it's never impossible. During the Soviet invasion of Afghanistan there was a confirmed case of a Mujaheddin downing a Hind attack helicopter by killing the pilot with a bolt-action Martini-Henry (i.e. late 19th century) rifle.
 * Generally averted during World War II, as better shielding for the pilot made it more efficient to destroy the plane's vital systems instead. However, the Japanese A6M Zero had a cockpit without armor protection which got many pilots killed when they went up against heavily armored American fighter planes.
 * Neutron bombs are designed to do this. A depleted uranium armored tank can withstand a tactical nuclear weapon detonated as close as a quarter-mile (400 meters). Depleted uranium will block blast, heat, gamma rays, poison gas, and pathogens. It is, however, worse than useless at shielding the crew from fusion neutrons, which instead of being captured or moderated by the armor, fast fission it, creating MORE radiation. Result: the tank is left intact, but the crew receives a fatal dose of radiation, and ideally at least 5-10 times the fatal dose (radiation poisoning kills slowly if you receive only one fatal dose, leaving the crew able to fight in the interim, but 5-10 fatal doses quickly cripple the victim and leads to a swift death).