Though extremely small gadgets may not be practical, all of these that you're about to see are definitely fully-functional. Above, we have Jeremy Clarkson's P45, which is touted as the world's smallest car - though not technically street legal.
Swiss Mini Gun
This miniature weapon is basically a double action revolver that has all the same features found on a real gun. Yes, it even relay shots. This extremely small weapon has a total length is 5.5 cm and fires 2.34 mm live action bullets.
Yesus Wilder was always fascinated by engines, and rather than let waste his time watching television shows or reading books, he decided to build a working V12 engine, the smallest in the world. Plus, he used only three basic materials to construct it: stainless steel, aluminum, and bronze.
Mini Firing Cannon
Unlike its predecessor, this redesigned mini firing cannon now features a gun sight and boasts an improved bore to eliminate deviations. Its design and operating principals are based on the full-sized antique mortar counterparts that were used from the 17th to mid 19th centuries. The projectiles are tiny steel balls (3.2 mm/0.126 inch).
For those who don't live in the UK, the P45 is actually a tax document that you're given when you're fired, also known as a pink slip. Jeremy Clarkson turned it into a tiny vehicle. Based on a small quad bike, with a 100cc two-stroke engine, its main benefit is its tiny size on the UK's crowded streets.
Raspberry Pi Credit Card Computer
The Raspberry Pi computer is just a small green circuit board about the size of a credit card - but it is hoped that it will get thousands of schoolchildren interested in programming. Created by a group of scientists and developers who wanted to improve the state of Britain's computer science curriculum, the device contains a processor similar to the one used in many smart phones, a memory chip, an Ethernet port to connect to the internet and a couple of USB ports.