Q
Q is the man that is behind all of 007's gadgets.
I am assuming that the name Q comes from the fact that he is in charge of Q-Branch, where all the gadgets are developed.
Q's (Desmond Llewelyn) full name was Major Boothroyd.
Q was in all the James Bond films from From Russia With Love, to The World is Not Enough
(Major Boothroyd, is in Dr No, but is not played by (Desmond Llewelyn)