Liquid Metal Alloy.
This is a metal that's liquid at room temperature, and it's not mercury. Instead, it's a mixture of gallium, indium, and tin, similar to the alloy Galinstan which is now replacing mercury in thermometers. You can buy little bottles like this from scitoys.com. Source:Simon Quellen Field Contributor:Simon Quellen Field Acquired:13 February, 2007 Text Updated:14 February, 2007 Price: Donated Size: 1" Composition:GaInSn