Aedes aegypti, the #1 disease vector for dengue fever (Photo by Muhammad Mahdi Karim, published under the GNU free documentation license)
War, plague, famine, heart disease, cigarettes, road trauma: six very effective killers of human beings. But they're all amateurs when their records are compared to the number one mass murderer of all time. The humble mosquito, and the deadly diseases it carries, is estimated to have been responsible for as many as 46 billion deaths over the history of our species. That staggering number is even more frightening in context - it means that mosquitoes are alleged to have killed more than half the humans that ever lived. So if any species deserves the full wrath of human technology, this is the one. And here, it seems, is how we might take our revenge - genetically modified strains of mosquito that are designed to cripple their own offspring and systematically destroy entire populations. And these mutant, auto-genocidal mozzies are already loose in the wild.