Mine used to be my Palm Pilot, but that's been replaced by my 7-sheet Cross Cut Paper Shredder that also shreds credit cards (and CDs if you cut them in thirds).
I bought it after someone opened a fraudulent bank account in my name using information obtained from the trash less than 3 weeks after we were notified that someone ELSE was able to incur credit card debt and purchase two cars in my wife's name using mail that we had ripped but not shredded.
Luckily, I knew how to prove without a shadow of a doubt that we could not have opened or used the accounts in question. But now, we shred anything that has our name or identifying information (account number, etc.) before it is thrown out.