Take a hammer to it. That's one sure-fire way... if you really want to be thorough, and if you have the right screwdriver bits, take off the top cover and run something sharp across the platter(s). [strike]Put it in the microwave.[/strike] Set it on fire. Power drills work wonders, too. There are lots of creative ways to destroy a hard drive.
In all honesty, unless you're trying to hide something from someone with an extensive ability to do data recovery (...like law enforcement...), just run
DBAN on it, cause a little bit of physical damage so that it isn't readily usable, and toss it. No normal person will ever be able to get any information off of it.