In the 50s there was The Third Man, starring Orson Wells and Joseph Cotton. Yes, dear children, they did make great movies before you were born. In the 60s we have Michael Caine as Harry Palmer, Deighton's "spy with no name", in two terrific films. Name them off the top of your head and give yourself a lollipop. Then there's James Bond, of course. But also, Alec Baldwin in the Hunt for Red October. And Leonardo's work in Body of Lies...equally exemplary.
But I already know my favorites. Let's hear yours!