We once took apart an ancient HP hard disk - you know the ones that were about the size of a small desk. The magnets were powerful, like these, and my friend got a finger pinched. I think he was lucky, could have been very bad. Put the like poles together, and watch the lighter chunk go flying across the room. The disks made nice shiny frisbies, but they were sharp, and would bury themselves in a piece of wood. You couldn't catch them without cutting your hand. Holy shuriken, batman!