My favorite metal is magnesium. I really like the way it looks when it burns. I'm guessing this would change if I got to see gallium or indium, but sadly I have never seen them
You're gonna laugh at my favorite nonmetal, but I just love it. Sulfur. It's so innocent looking, yet it forms pretty dangerous compounds like the incredibly caustic sulfuric acid, and the deadly poison hydrogen sulfide. Phosphorus is also a very cool nonmetal. Oxygen is cool too, particularly in liquid state.