Onion, garlic, leek, chives
This family of foods contains components that will destroy red blood cells in cats, which will trigger anemia and jaundice. A few grams are enough to be toxic. Watch out for baby foods that contain it.
Grapes and grapes
Responsible for kidney failure without knowing how, grapes and their grains are toxic to your cat.
It contains highly toxic methylxanthine. Dark chocolate is even more concentrated of this substance. Doses of 2 grams of dark / dark per kilo and 10 grams per kilo of milk chocolate are sufficient to be toxic.
This list is not exhaustive and other foods can be toxic to your cat (or your dog). It is important to understand that they are not made like us human beings and are not able to digest the same ingredients.