1. Chocolate...It stimulates their heart and nervous system. And it's dangerous for all species of pet, but especially dogs.
2. Grapes or raisins...Both are poisonous to cats and dogs because they can damage their kidneys.
3. Garlic and onions...They can cause anemia in cats and dogs.
4. Macadamia nuts...These can cause muscle and nervous system damage in dogs.
5. Avocados...These are harmful to most species, but especially birds. They can damage the heart muscle.
6. Alcoholic drinks...This seems like a no-brainer, but alcohol is bad for ALL species because it depresses their nervous system.
Source: Real Simple