Rather than hijackthis thread,I thought this might merit it’s own.
From that thread:
Microwave oven, 5 seconds. A little smelly, but fun to watch.
They also make fun targets for plinking if you are into guns.
I’ve also seen them suspended over gardens and freshly planted lawns to scare away birds…not sure if that works or not. (and it is not really a secure disposal solution as Leaper was seeking)
What else are they good for?
Wouldn’t a little sandpaper make it unreadable? Or would it just make it harder to recover?
Doesn’t pose a secure solution, but for less-sensitive data (old music CDs or AOL freebies etc.), we turn 'em into pretty Christmas wreaths with a hot glue gun 
Some shredders will destroy CDs. I’d imagine that just breaking them by hand would also do the trick, but I’d want to verify that before relying on that method for really sensitive data.
If you’re looking for off-label uses for old CDs… Maybe coasters or hotpads? Or, flinging them like a discus could make for a potent weapon.
I made the border frame to a mirror out of them once…
Some of the suggestions here might be of interest.
Use it as a Frisbee. While going 75 down the interstate. 
I send all the annoying “Get 1000 Free Hours Of AOL” discs and their ilk to my mother to give to her best friend’s grandson. Why? He wallpapers his bedroom with the shiny sides.
Arts and crafts! Instructables.com has some ideas for a CD fish, dodecahedron and snowflake ornaments made out of CD’s and many more. Although they may not result in complete data loss but is someone really likely to take apart your CD fish to read your secrets?
The information is underneath the label side, so you’d have to sandpaper that side. If you do the other side, someone can just polish it down until it’s transparent again and get the data.
Some suggestions here .
Sometimes kids have to make rubber band or mouse trap powered cars. The CDs make great back wheels. You just have to glue a rubber band to the rim for friction.