Government agencies have looked into using animals as secret agents, and have even wired up a cat to try their luck. But I think coolest-looking spy animal ever must have been a raven.
Ravens have advantages as spies; they're solitary, but also common enough to blend in nearly everywhere. Being corvids, they're smart, and can be trained to do many things.
Some ravens were audio spies only. They could carry radios in their mouths, swoop up to a window, put the radios down, and fly away. To retrieve the bugs, they simply flew back up, picked them up off the window ledge, and returned to their handlers. The ravens could be directed to any window with a laser pointer. (One assumes that the person with the laser pointer was careful. If I were doing something in a room that spies were interested in, and suddenly saw a laser sight on me, my Secret Spy-worthy Meeting would be over quickly, and the raven's recording device would capture nothing but screams.)
Then there were the camera ravens. They could hold a small camera in their mouths, and press it up to the window of a building. When the camera was pressed to a surface with a certain degree of force, it would take picture. There isn't any real evidence that these birds were used. Ravens are, generally speaking, too big to ignore, especially if they're fluttering at a window. And pictures taken by ravens would be blurry and randomly directed at best. I bet they got a lot of pictures of floors and light fixtures.
Still, it's cool to know that the animal kingdom was once a giant Bond film. And from now on, if a bird starts looking at you funny, you can guess why.