Neodymium Magnets

If you happen to have some liquid nitrogen you can turn a handy dandy hunk of ceramic into a superconductor and do really strange stuff. Check this movie.

Of course if you want to skip the absolute zero superconducting material you can just order really cool, really big magnets from here. The 3 x 1 inch one is one of the most powerful magnets available. From their warning - "two of (these) magnets can easily break your arm if they get out of control."

Shipped by ground only - screws up aircraft navigation equipment. Oh, and the normal shipping staff won't ship 'em - they make the Top Men do it. Only $100 - what a deal!

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Previous related Wohba links:
They also sell ferrofluid.
Other fun with liquid nitrogen.