You can make a demagnetizer. All standard precautions about handling electricity apply.
You take the transformer out of a dead microwave, saw the end off, slide out the secondary coil. At this point you discard the secondary coil - you don't want to play around with the 5kV that comes out of that. Keep and use the power supply board from the microwave - it has the convenient cord, plug, and should have a fuse to keep you safer using this.
What's left is a primary coil sitting in a big "E". Face the 3 legs of the E pointing up. Rest your magnetized object on them. Plug in the transformer for a moment and unplug it. Half the time when you unplug it, your object will be demagnetized. The other half of the time it's become magnetized, so just do it again until the mag field is gone.
Since it can magnetize and demagnetize, you can re-magnetize your screwdrivers with it, if you like.