This is not a complete list and some dogs tolerate more than others. Please comment if you think we forgot something 🙂

Almonds – they can get stuck in the windpipe and even puncture it

Salt – Increases fluid retention and can cause death in breeds that have a known heart problems

Cinnamon – cinnamon and its oils can irritate the dogs mouth and cause discomfort. Cinnamon can also lover the blood sugar, cause arrhythmia and liver diseases

Onions and garlic – can cause anemia (pale gums, increased heartbeat, shortness of breath and more). Onion/garlic poisoning doesn’t show right away so you need to keep a close eye on the dog for some days

Ice cream – generally contains dairy products and dogs have a hard time digesting lactose. A better option is to freeze strawberries, apples and pineapple and feed that to the dog on a hot day

Macadamia nuts – these nuts are really toxic for dogs. Can cause vomiting, increase the body temperature and cause damage to the nervous system

Chocolate – chocolate contains ingredients that can cause diarrhea and vomiting even in small dosages. A lot of chocolate can cause seizures, irregular heartbeat and even death

Fatty food – the fat can cause pancreatitis. Small breeds are more vulnerable

Salt – salt can cause poisoning in dogs, irritate their stomachs and they could consume dangerous amounts of water after eating salt. This also applies to salty food

Cheese – same as ice cream, usually contains dairy products that can cause problems for dogs

Xylitol – lowers the blood sugar levels and can cause liver failure

Sugar – can have the same effects as on humans, obesity, dental issues and diabetes

Avocado – the stones can get stuck in the throat and cause suffocation. Avocado contains persin which is in large dosage poisonous for dogs. The leaves, bark and fruit all contain persin and therefore it is wise to keep avocado plants out of reach for dogs

Alcohol – dangerous for dogs and can cause death

Apples – ok in small quantities but it is best that the dog doesn’t eat the core and the seeds

Cat food – contains too much protein and fat for dogs. Better suitable for cats

Salmon/trout – raw salmon/trout can contain parasites that can be lethal to dogs. Cooked salmon/trout is ok for dogs

Peaches – the stone can cause suffocation and the fruit contains substance that converts to cyanide when digested

Pears – contain small amounts of arsenic and are therefore dangerous to dogs

Rhubarb – contains oxalates that can influence the digestive system, the nervous system and the urethra

Yeast – expands in the stomach and can cause upset stomach and gas. In large quantities the stomach can burst

Grapes and raisins– your dog may have eaten a grape or raisins without any consequences but a very small quantity can cause kidney failure and death

Caffeine – can cause arrhythmia and muscle tremors

Here is a cool infographic from Petworshiper to summarize.

Resources:
http://internet.is/tjica/bannad_ad_borda.html
http://www.akc.org/expert-advice/nutrition/natural-foods/human-foods-dogs-can-and-cant-eat/
https://www.caninejournal.com/foods-not-to-feed-dog/
https://yourdogadvisor.com/can-my-dog-eat-this/