Orcas possess awesome speed, power and intelligence, but the rattlesnake, black widow spider and even the mosquito challenge them in dangerousness.

Despite dwindling numbers, the Humboldt squid's beak is deadly, but the Brazilian wandering spider's fangs and venom are ruthlessly efficient.

Creatures such as the tarantula and the Gila monster are nightmares of myth and legend -- but also a surprising treasure trove for medical science.