This is easily the best Silly Putty ever, and that's hard to do, because Silly Putty is the best toy ever:
It's temperature sensitive color changing silly putty! Awesome!
[$3, Office Playground]
[Via Mighty Goods]
okay, i had this as a child and here's the problem: you're 5 years old and you figure out that hot things make your silly putty change color... logically something really warm (radiator, lamp, tea cup) would also make your silly putty change color. Really warm things make silly putty melt. And get everywhere. And now your parents are unhappy.
@bee: ...and now i have to try that.