Just hook onto the voice coil as if it were a speaker and pipe some analog signal at it. Heck, pipe some music at it. Literally any magnetic-platter hard drive will work - from the first one to the ones they'll be building Next Tuesday. You just might be surprised at the result - they're actually quite good speakers.
If you're looking to use them as a percussion insturment, just throw them all the way to the bump-stops for a satisfying CLACK.
The easiest way to get access to the voice coil is to pop off the PCB on the bottom (discard it, harvest it for parts, whatever) - that PCB will mate to either a ribbon cable or terminals at two spots: the hub of the main spindle, and a second set with 4+ pads near the hinge for the arm. Poke around on those 4 pads (I recommend using bare speaker wire connected up to a nice, loud radio) and eventually you'll find it the right two connections. You don't need to apply any power at all to the hard drive unless you want to pin up the platters - a lot of drives make some pretty cool sounds on spin-up, so you may want to look into that, too. The spindle motors usually respond well to 12vDC.