Welsh actor Desmond Wilkinson Llewelyn (Born: September 12, 1914 - Died: December 19, 1999) featured as gadget master Major Geoffrey Boothroyd – alias ‘Q’ in 17 of the 19 James Bond movies , spanning an incredible 36 years.

Desmond has appeared in:

From Russia With Love (1963)
Goldfinger (1964)
Thunderball (1965)
You Only Live Twice (1967)
On Her Majesty’s Secret Service (1969)
Diamonds Are Forever (1971)
The Man With The Golden Gun (1974)
The Spy Who Loved Me (1977)
Moonraker (1979)
For Your Eyes Only (1981)
Octopussy (1983)
A View To A Kill (1985)
The Living Daylights (1987)
Licence To Kill (1989)
GoldenEye (1995)
Tomorrow Never Dies (1997)
The World Is Not Enough (1999)

Desmond Llewelyn did not make an appearance in:

Dr.No (1962)
Live And Let Die (1973)

John Cleese

Cleese was cast as Q's deputy 'R' in The World is Not Enough. Following the sad death of Desmond Llewelyn in a car accident, Cleese has taken the title 'Q' for Die Another Day.
Famous for his roles in Monty Python and Fawlty Towers, John should suit this role perfectly.

Q's best quote from Die Another Day:
James Bond: You know, you're cleverer than you look!
Q: Better than looking cleverer than you are.

“Right now, pay attention!”

gadget (gajit) n. 1. A small specialised mechanical or electronic device; a contrivance. 2. Any ingenious device, especially one that is labour-saving.

Little Nellie: this waspish autogyro saves Bond’s bacon in You Only Live Twice when he’s set upon by a fleet of SPECTRE bad guys’ helicopters. Literally a flying arsenal with a lot more than a sting her tail : 2 fixed forward-firing machineguns synchronised to 100 yards – using incendiaries and high explosives; 2 rocket launchers forward-firing on either side; heat-seeking air-to-air missiles – 60 a minute; Flame guns – 2 firing astern, range 80 yards; 2 smoke ejectors; Aerial mines; Cine camera in pilot’s helmet; Radio tuned to 410 megacycles.
After vanquishing the foe 007 sends this message: “Hello Base One – Little Nellie got a hot reception. Four big shots made improper advances towards her – but she defended her honour with great success.”

Hasselblad Camera Signature Gun: this deadly gadget really does have a viewfinder to a kill! The film magazine contains a magazine of .220 high-velocity bullets, while its tripod-like attachments screw into the body to form the butt and barrel of a deadly sniper’s rifle. The handle of the gun also contains an optical palm reader, ensuring only the person programming the computer sequence can fire the weapon at a later date.
In Licence To Kill, Bond uses the Signature Gun (one of Q’s most ingenious and lethal gadgets) in an attempt to avenge the murder of his best friend’s wife. On this rare occasion, 007 misses his target, South American drug baron Franz Sanchez, when he is overcome by a group of Ninjas.

Parker Pen Class 4 Grenade: on this occasion, thanks to Q, the pen is indeed mightier than the sword! 3 clicks of the pen arms its 4 second fuse, while a further 3 clicks disarms it. The writing’s on the wall for treacherous ex-British agent Alec Trevelyan (006), when Bond uses this harmless-looking everyday object to prevent Trevelyan from using the Goldeneye satellite to devastating effect.

Snooper: a robot ‘dog’ whose movements are controlled by remote control. Snooper transmits video images via its eyes. It also has a telescopic neck for peering over or around objects obstructing its view.
While searching for 007 with Snooper at the end of his mission in A View To A Kill, Q is shocked, but hardly surprised, to find Bond sharing a shower with heroine Stacey Sutton. Oh James!