The sneaky thing about chocolate is that it is cumulative. Give the dog the same chocolate you give it every day, and one day it gets very sick and dies. If it eats a candy bar, the raisins in it could kill it quicker than the chocolate. Some dogs are very sensitive to grapes and raisins. The vet didn't mention wine.
The Xylitol in sugar free gums is bad too. Stimulates the production of insulin, and the blood sugar tanks.
The last item in the vets talk I listened to last summer was bottle caps. Tears their insides up.