For under $10 you can get one of the coolest silly (style) putty's around, magnetic thinking putty. This "thinking putty" is embedded with millions of tiny micron-sized magnets so it does some pretty cool tricks. Cool videos after the break.
"Thinking Putty is a crazy, non-toxic substance that you can stretch, bounce, shape, tear, and shatter! The Thinking Putty can help to reduce your stress and you’ll have fun doing it. It’s a lot more useful than doodling because you can exercise your hands at the same time! — Black and mysterious, this Thinking Putty definitely sets your mood. It also responds to a magnet. Simply pull a strand out and hold a magnet nearby. This color will pull itself right up to it! Lay it on an incline and put a magnet underneath for a cool effect. The stronger the magnet, the better the result."