How to permanently decommission a security token?

The CARS Cash for Clunkers program requires gas guzzling trade-ins to be permanently decommissioned by replacing the motor oil with a sodium silicate solution.
The Cash for Security Tokens program is looking for the best method to decommission tokens traded under the program. Anyone who has been frustrated by a lost or out-of-sync security token has probably already thought of a few ways.
Submit your suggestions for how best to kill a security token.