It can cause vomiting, diarrhea, decreased coordination, central nervous system depression, difficulty breathing, tremors, abnormal blood acidity, coma and even death.
Chocolate, Coffee and Caffeine
They can cause vomiting and diarrhea, panting, excessive thirst and urination, hyperactivity, abnormal heart rhythm, tremors, seizures and even death.
It can cause irritation and possibly even central nervous system depression if ingested in significant amounts. Small doses, such as eating the fruit, are not likely to present problems beyond minor stomach upset.
Grapes and Raisins
Although the toxic substance within grapes and raisins is unknown, these fruits can cause kidney failure. Until more information is known about the toxic substance, it is best to avoid feeding grapes and raisins to dogs.
Milk and Dairy
Because pets do not possess significant amounts of lactase, milk and other dairy-based products cause them diarrhea or other digestive upset.
Those are just to name a few. Here is the link to see additional foods to avoid feeding your pets.