Art of paper folding. In order to obtain a nice and effectiveness result, put the floppy in the disk drive after folding it several times in different directions. With a little luck, you should be able to get it jammed. Now, ask yourself. How can your disk get damaged if you can't even get it out of the drive?
SMOKE
Use cigarettes or anything that could be burnt. When you are smoking, blow directly to your disk. In that way, you will be able to destroy it soon, and if you are lucky, damage the drive as well.
PIRANHAS
If you don't have any at home, you can use a stapler, a clip, or simply write down on the disk label with a hard point pencil or pen. This wonderful method of "caring" for disks also often gives you a pretty bite-like design on the remaining pieces of the disk.
MAGNETS
They are wonderful. You can find them in the telephone, in some paper weights, and stuck on the frige door. If you can't find any, you can leave the floppies on the printer or on your display for a while, making sure that they are on.
Put a disk in an envelope and don't write any warning on it; then mail it to someone, and that's all.
MAGIC TOUCH
Touch your floppy. As much as you can. If you have marmelade or butter in your fingers, better. Your floppy will acknowledge it.
DON'T USE ANY ENVELOPE
Archive them wihtout their envelope, piled under a lot of papers and manuals.
DON'T MAKE BACKUPS
Of course, if you don't have any security copy, you won't have to worry about how to destroy them once you have lost the original.
SUPREME STUPIDITY
It is the best way of destroying floppies. If you practice it regularly, you'll find new methods to add to this list.