Shall we open with an ironic reference to Terminator 2? Best not. That's the easy option, especially when dealing with lumps of metallic ooze that seem able to alter their shape in response to their surroundings.
Magnetic Thinking Putty is your standard play putty, only stuffed with "millions of tiny micron-sized magnets" to ensure it responds to any other large magnet. Including the one that comes in the box. Here's a video of Magnetic Silly Putty absorbing its cubed magnet. It doesn't move quite as fast as Robert Patrick sprinting after your car. [Vat 19 via OhGizmo]