In the winter they tend to climb up inside car engines where they can be subsequently ground up. Anti-freeze is extremely toxic and your cat will die a painful death within hours of ingesting it. Poisoning - There are people who don't like cats and will set out poison on their property. Others may put poison out to get rid of other wildlife that wanders onto their property and your cat may accidentally ingest it. Fighting - Your cat could be killed by dogs, raccoons, or other wildlife.
Some people train their dogs to attack and kill cats.
Fighting Part II - Believe it or not, cats can kill each other during their fights. FELV - Feline Leukemia destroys a cat's immune system. It is transmitted through body fluids. Even a sneeze can pass the virus from one cat to another. Cats infected usually die within two years.