From the Caribbean comes a threat so unexpected, but frighteningly genuine. The Hippomane Mancinella tree is one of the deadliest in the world. Every part of this living hazard could potentially kill or cause serious illness: The thick milky sap can burn skin, whilst its small round fruit is poisonous and any contact with toxic bark is strongly unrecommended. Don't lit a fire with its wood because the smoke is venomous and don’t stand anywhere near the tree when it rains.