A metal, with the chemical symbol Ti.
Due to its excellent strength-to-weight ratio and high corrosion resistance it is used to make some of the most Gucci, shiny and expensive kit currently available. Despite the fact that it's actually a dull grey colour titanium is currently only exceeded in its shininess by carbon fibre and really obscure stuff like PEEK, MMC's and fullerene fibres.
Frequently used in the aerospace industry, the SR-71 Blackbird was built almost entirely from titanium. The plane was so cutting-edge that new forging processes had to be developed as these were the largest parts ever manufactured from titanium at the time. I'm sorry, I need a lie down...
...That's better, where was I?
Somewhat bizarrely, the titanium used to build the SR-71 was sourced from the world's largest supplier at the time - the Soviet Union.
Pub bore factoid #1547 - by far the principal use of titanium is Titanium Dioxide, the most common white pigment. Check the ingredients on Mint Imperials.