Africanized Honeybees (killer bees)
How they kill: Found in Texas, California, and other parts of the Southwest, Africanized honeybees are slightly smaller than their European cousins but far more hostile. Apt to unprovoked attacks in response to disturbances up to 50 feet away from their nest, a swarm could fly into your home through an open window or door just because they don't like the sound of your radio or power tools. Running is the recommended defense, but unless you're an Olympic sprinter, that may not be enough to save you: The swarm will fly in hot pursuit for a quarter mile, catch up with you, and begin stinging in great numbers, which can be fatal to someone with allergies or pre-existing health problems.
How to get them before they get you: To discourage colonization on your property, seal cracks in your house and discard items that would provide shelter for a nest—such as tires or terra-cotta pots not in use. Look before you disturb bushes, flowers, and plants. Report any swarm found near the home to pest-control operators and/or beekeepers, and do not go near it or attempt to move it yourself.