While some of the equipment dreamt up by Q is clearly fictional, there are some parallels between James Bond gadgetry and true-life spy equipment. The key difference between 007 and a real-life secret agent is in their overall approach to their missions. Spies in the real world are primarily focused on stealth and gathering information. More rarely, they are used as assassins, but even then they use subterfuge to quietly accomplish their deadly mission. So anything James Bond uses that fires missiles, uses acid, has concealed machine guns, launches with great velocity or simply explodes is unlikely to have a counterpart in real life.
The glaring exception is his gun. The Walther PPK is, in fact, heavily favored by covert operatives even today. Originally designed for use by plainclothes East German police, Fleming replaced Bond's small-caliber Beretta with the Walther and a Smith & Wesson .38 at the request of Geoffrey Boothroyd. Boothroyd was a gun expert and Bond fan who wrote to Fleming in 1956 to recommend the use of more appropriate weapons. Fleming eventually honored Boothroyd by naming the character Q after him.
True-life secret agents usually favor small-caliber handguns because they are easy to conceal. However, in situations where greater firepower, range or accuracy is needed, special rifles or machine guns can be made to fold down or disassemble into smaller components that are easy to hide. During World War II, the British Sten submachine gun was provided to French resistance operatives and other Allied spies -- it could be collapsed into three pieces for hiding. Guns can also be equipped with silencers, metal cylinders that baffle the rapid expansion of gases and greatly reduce the sound a gun makes when it fires. Another form of silent weapon is the crossbow. These weapons eliminate the need to smuggle bullets and don't produce a muzzle flash when fired.
Spies have used very Bond-like concealed, single-shot weapons disguised as common objects. A tiny pistol that can fit into a belt buckle, a cigarette that could fire a single .22 caliber round when the operative pulled a string with his teeth, a single-shot pen gun and a wrist-holster that could fire with a single arm movement were all actually used. Guns were also concealed in flashlights, gloves, pipes, pencils, tubes of toothpaste and rolled up newspaper.
Two of the most surprising real-world assassination devices were disguised in a pack of cigarettes and an umbrella. The cigarette pack was to be offered to the victim, aimed near his face as if to let him draw a cigarette out with his teeth. At that moment, it would be triggered, ejecting a cloud of cyanide vapor into his face, killing him very quickly, and with almost no trace evidence. The would-be assassin had a change of heart, warned his target, and defected.
A more successful assassination plot used an umbrella containing a pneumatic firing mechanism and a small poison pellet. The target was Bulgarian dissident Georgi Markov. The assassin shot Markov with the pellet while he stood on a bridge -- the incident was passed off as an accidental bump with a pointy umbrella. Markov grew sick and died days later.
Q's habit of hiding useful (generally explosive) items in everyday objects is closely mirrored by the activities of real-life spies, although hidden weapons were much rarer than more practical concerns. Spies hide and smuggle cameras so they can record vital information, and they hide the information itself for transport back to their superiors. The Latvian-made Minox camera remains a vital piece of spy equipment even 50 years after its manufacture. The camera is small enough to conceal in the palm of your hand. Many spies used a microdot camera, a device the size of a thimble that was easy to hide. It produced very tiny images that required a magnifying viewer to read. Photographic devices were hidden in wooden statues, chess boards and other objects.
Information itself, especially in the form of microdots, could be hidden virtually anywhere. Film was stashed inside fake coins, fake batteries with hollow middles (with a real, functioning battery inside), shaving brushes, cigarettes, shoe heels, ashtrays, bolts and nails -- even a fake eyeball. In many cases, these items had a mechanism that would release a small amount of acid if it was opened improperly. The acid would destroy the film, saving the spy from detection in the event of a thorough search by suspicious enemy agents.
One thing real-life secret agents don't use is a flashy car. The last thing a spy wants to do is draw attention to herself. The car used for a mission will be typical of whatever the general populace in the area drives, and it will be as nondescript as possible. It will certainly not contain missile racks, smokescreen dispensers or have the ability to turn into a submarine. At most, a real life spy's car might contain hidden compartments for storing information.