Moderate to high toxicity holly berries and leaves; bubbling lights (methylene chloride); snow scenes (may contain salmonella); aftershaves / perfumes / alcoholic beverages; and chocolate (dark is more toxicthan milk).
The darker the chocolate, the more dangerous for canines: A single ounce of baking chocolate is toxic to a 10 — pound dog, though she can consume 10 ounces of milk chocolate without serious consequences (other than a possible upset stomach).
Cats are less likely than dogs to chomp down a toxic dose of chocolate, but it's still best to keep it away, especially darkerchocolates that contain more cocoa.