Garlic and onions (cooked and raw) - often in gravy. Do not give garlic supplements for deworming/fleas - this does not work and is toxic.
Grapes and raisins - very toxic, even a few can cause kidney failure.
Paracetamol (panadol), ibuprofen (nurofen) and aspirin - these are the most common human medications given to animals, unfortunately even one tablet can be harmful.
Alcohol, bread dough
Raw potato, avocado, macadamia nuts.
Chemicals - ethylene glycol (antifreeze), fertilisers, pesticides, disinfectants including bleach, detergents and antiseptic fluids/lotions. Do not use human antiseptics, creams or bleach to treat wounds - this can get absorbed or they can ingest it by licking.
Plants - including lilies, pine, acorn, bracken fern, macrocarpa.
Bones are not toxic but can be very unsafe. We often see broken teeth, but worse many dogs become obstructed and need immediate surgery. We also see food poisoning and constipation from bones being fed. If you do feed them ensure they are fresh and not cooked (cooked bones become sharp shards when crunched down), and try to prevent your dog from swallowing chunks of bone.