In movies we often see spies using awesome equipment from exploding pens to knives on shoe tips. Most of them are obviously made up but cases like the infamous risin poisoning through an umbrella in the 70s prove that there must have been developed some items that have even seen action. I think I can safely assume, that there is only a very limited number of documented cases on this matter, so I would love to hear about any spy gadgets that were in use throughout history.
The International Spy Museum covers many of these topics and has done some podcasts on the subject (theirs are called Spycasts). They're a great history resource for espionage and are not afraid to happily tap into spy pop culture like James Bond and Smiley. I just heard a couple of days ago that they're selling Archer merch in the gift shop.
There is a great book called Spycraft. I'm on my phone and can't look up info at the moment. The author world for the CIA. I believe he wrote a follow up as well.