The Cockroach
It is widely believed that cockroaches are capable of surviving a nuclear war. Whilst they are not as resistant to the effects of radiation as some other insects, it is true that they are fifteen times more resistant than humans. Cockroaches also have other amazing abilities, like being able to go without oxygen for up to 45 minutes. They can also survive without food for a month and are capable of eating almost anything, including the glue on the back of stamps. It's not pretty but if it works don't knock it.
To date, around 4,000 distinct species of cockroach have been identified.