One animal certain to be far more terrifying to men than to women, the pacu is a much larger relative of the piranha, known for its distinctive, human-like teeth. Unlike most of the creatures on this list, the pacu is actually omnivorous, and a good part of its diet is comprised of fruit and nuts. Unfortunately for some pacu, “nuts” may not only mean things that drop from trees. Yes, that’s right: Pacu are alleged to have occasionally bitten off the testicles of male swimmers, with reports of men in Papua New Guinea being killed by pacu after the fish apparently mistook their genitalia for an easy snack. Oh, and don’t worry if you can’t make it to the Amazon to see these manhood-masticating monsters, because they’re already spreading into Europe.