Yes, there are several types of weeds that are poisonous to humans or animals, either by ingestion or contact with the skin. Examples include poison ivy, poison oak, poison sumac, stinging nettle, giant hogweed, jimsonweed, and hemlock. These weeds can cause a range of symptoms from mild irritation to severe allergic reactions, respiratory distress, or even death. It's important to exercise caution when handling or removing these types of weeds and to seek medical attention if you experience any adverse reactions.