Funnily enough, my favorite gadget is from one of the most derided of all Bond films. The Wrist Dart Gun from Moonraker:-
Gadget: Wrist Dart Gun
Movie: Moonraker
Owner: James Bond
Status: Stored at Q-Branch
A dart gun the strapped under the user's wrist like a watch, was capable of firing small darts at the flick of a wrist. Bond was give two sets of darts, 5 poison tipped and 5 amour piercing tipped.
Use
Bond used the wrist dart gun 3 times, once saving his life. Firstly he tested it out in M's office by firing a dart into a painting. Bond's life saving came, when he was in a centrifuge, the control room was taken over by Drax's henchman Chang, who turned up the G's to a lethal volume. Bond flicked his wrist, firing an amour piercer into the overridden stop button, stopping the machine with a short circuit. Lastly Bond used a poison tip to kill Drax, firing it into his heart and forcing him though an airlock into space.
Specs
A small gun like device propelled the darts by using pressurised gas, good for 10 firings before refill. The poison tipped darts, were coated with concentrated cyanide, the amour piercing dart had cores of depleted uranium - like the ammunition used in large bore military machine guns.
My second favourite is from The Spy who Loved Me. The Lotus Esprit Submarine:-
Vehicle: Lotus Esprit Submarine
Movie: The Spy Who Loved Me
Owner: James Bond
Status: Stored at Q-Branch
The Lotus Esprit was perhaps the most advanced car Bond has driven, it had the capability to transform into a submarine, and an array of other ingenious gadgets. The Lotus was personally delivered to 007 in Corsica, driven by Q, who warned Bond to be careful with the car. Bond responded to Q with a smart remark, dropped the clutch, and took off with a grinding screech.
Use
The Lotus Esprit came to be very useful for Bond during The Spy Who Loved Me mission, while being chased by Jaws, Bond used the concrete guns to spray the windshield of Jaws' car causing him to crash. After getting Jaws off his tale, Bond was being chased by Naomi in a helicopter armed with machine guns. Much to Anya's shock Bond sped down a dock and drove off the end into the sea, surprising Anya when transforming the car into a submarine, with tail fins, a periscope and a submarine control panel. Bond shot Naomi out of the sky with a sea-to-air missile, and was then chased by Stormberg's men in small subs, who tried to destroy the Lotus, but Bond used an oil slick as camouflage, and fired back with missile's, destroying the subs.
At the conclusion of the battle, Bond found a hole in the roof of the Lotus, and water was leaking in, in an emergency he drove the car out of the water. As he emerged from the water onto a beach, with bystanders in staring in disbelief, Bond wound down the window and threw out a fish that the car caught through the leak in the roof.
Specs
White Lotus Esprit, number plate "PPW 306R", with the following modifications:
Submarine Features
Retractable wheels, with extendable covers to protect the wheel cavity
Retractable fins and rudders for underwater steering
Convertible dashboard to double as a submarine control system
Radar and Nautical guidance equipment
Metal blinds for rear window
Four retractable propeller units at the rear of the car
Weapons & Defence
Surface-to-air missiles
Underwater mines
Oil-slick sprayer for underwater camouflage
Rear mounted concrete sprayers
Harpoons for underwater combat
Self destruct system
TV Monitor and closed-circuit camera
Periscope