Nitinol wire in the shape of the word HOT
When the wire is cold, you can bend it into any shape you like. When you then heat the wire above about 40 degrees Celsius, for example in fairly hot water, the wire will spring back into the position that has been set in its memory, so spelling the word HOT. To repeat the trick, just put the wire in cold water, or hold it under a cold running tap, and you can then bend it into whatever shape you wish. John Davenport bought this from Grand Illusions Ltd (www.grand-illusions.com) in 2008.