The Ipcress File (1965) is one of those movies you see mentioned a lot, especially in conjunction with the name "Michael Caine", but I'd never actually seen it, myself. Just as Bond movies were taking off, Bond producer Harry Saltzman decided to launch a competitor to Bond's sexy, sly cartoonish spy adventure and gave us a spy somewhere between Bond and George Smiley.* His world is not about bureaucracies being very sneaky against each other, nor is Harry Palmer going to drive a high end sports car with a smoke screen and rockets, either.
What really stood out for me, though, was that Harry Palmer - at least in this film (and he's in 3-5 films, depending on how you count them) - feels like a very real sort of person in comparison to James Bond. Chalk this up to Michael Caine's talents or a very clever script, but Harry Palmer is a semi-ne'er-do-well who is happy having a government check, finds all this easier than working for a living, and is riding out this "spy" gig he's got going on until the gravy train runs out. In the meantime, he peeps on people and doesn't particularly care for the rest of the rubbish paperwork.
Until he's changed offices and put on a real assignment.