Mushrooms are among the foods that will either kill you or make for a delicious meal.
(In my childhood I had a book about berries with similar properties– ones that were dangerous and those that were edible looking so similar as to be distracting. The picture book was meant to be a cautionary tale, with the subtle illustrations pointing out differences any child could see.)
Most foods are not poisonous, of course, but adventurous eaters indulge in a Japanese delicacy called fugu, or puffer fish. It contains enough toxin to kill 30 adults and has to be prepared just so by trained and licensed chefs to be safe for human consumption.
Less well-known dangers lurk in our kitchens. Sure tomatoes are edible, even delicious, but the leaves contain a toxic alkoloid called tomatine; the plant of the tomato belongs to the nightshade family (as does the eggplant, another of my favorite vegetables). Rhubarb is another delicacy that can, alas, cause damage.