A passive low frequency PIT tag will continue to operate after it has been cooked in a microwave.
Tags are not damaged by strong magnets nor high voltage charges.
Many attempts have been made to stop a tag from operating. The most effective way is to either wrap it in metal foil or break the glass capsule and crush the tag assembly (beware of sharp pieces of broken glass!). It is possible to destroy a tag by heating it in a convection oven at a temperature that is high enough (400F/200C) to melt the solder on the wires inside the tag.