Intravenous Injection of Chemotherapy. It is very common for chemotherapy medications to be injected into a vein, or intravenously. In many cases, a nurse or doctor will insert a needle into your vein, often in your hand or arm, and the chemotherapy will be given through there.
2. Poison Dart Frog. Of all the poisonous animals in the world, these are probably the easiest to spot due to their extremely bright colors, including yellow, blue, green, & red. These frogs don't actually inject their poison through their mouth; they do it through their skin.
The bark is poisonous too -- burning it releases a smoke that causes temporary (and in some cases, permanent) blindness. Considering all the ways it can hurt you, it's no wonder the manchineel currently holds the Guinness record for world's most dangerous tree. Legend has it that one of the most infamous deaths by manchineel poison was of Spanish conquistador Juan Ponce de Leon.