Gold leaf you've probably heard of, but it's possible to get very thin sheets of several different pure metals: Click the Sample Group link below to see all the ones I have, which represent pretty much the complete list of those that are commercially available. (Many, many different mixed alloys are also available in leaf form.).
Leaf like this is so thin it has to be picked up with special Red Squirrel hair brushes (none of that Gray Squirrel crap, mind you) and when it wafts down onto an object it conforms to the shape of the surface, settling in even to details as fine as a fingerprint.
I bought this leaf from a store in New York when I was visiting there with my six-year-old daughter Addie: You can read about our visit here.
Source: Sepp Leaf Products
Contributor: Theodore Gray
Acquired: 11 July, 2003
Price: $65/500 sheets
Sample Group: Metal leaf