Garlic, onion. Apple core, peel, and almond have cyanide which if eaten in copious amounts can hurt them. I try to keep them away from citrus. I don't know if dogs and cat could eat them, but all I know is that other livestock can't.

Lillies are extremely dangerous. Just their pollen can shut down animals livers/kidneys. Forgot which. I have too many horror stories of a person purchasing lillies or given as a gift and their curious cat put their nose in the flower.

Another super dangerous plant are jade. Extremely dangerous. Also any in that family (i think crassula?)