First things first: when we say top secret here, we can be forgiven for being a little facetious. After all, some of the weird and wonderful projects in this article date back to World War II, and security clearance tends not to be an issue for seventy-year-old military secrets.
But just in case you consider it impossible for a pop culture website to have access to information on a genuinely top secret weapons programme, we should point out that in 2013, around four million people were considered to have top secret security clearance in the United States alone, including half a million private contractors. Thats a whole lot of potential whistleblowers with a broadband connection and a Reddit account.
This article doesn't represent an exhaustive list, or a top ten: we've compiled a selection of military programmes, some modern, some a little more old school; some successful, some utter failures, and some still in the final stages of development.
The main criterion for inclusion is that they raise an eyebrow or two. After all, we like to think we know how the world works, but some of these classified projects are a little out there. We skipped over the Russian initiative for using exploding dogs to take out tanks in World War II, poor little blighters. Others, well, see for yourselves.