bbum runs down some great ideas for removing all traces of your data from an old hard drive:
Me? I take dead drives apart. They have amazingly powerful magnets inside, along with all kinds of very useful screws, washers, nuts, coils, and other fiddly bits.
The platters, obviously, contain the data and they should be destroyed. I run one of the magnets over them upon removal and then keep a stack of the platters around as they have proven to be incredibly useful! The platters have been used for everything as clamp pads for gluing stuff to spacers to level a table or work surface to being used by my son as part of a bug house.
But the best of all has to be the one shown in his photo shown above: “Set up a high speed photog kit and drop a pinball on it!” Link