6. Severus Snape
Snape: the one everyone loved to hate and then cried for about a fortnight after his horrific death. He was of course Potions Master extraordinaire (with an uncanny ability to interpret recipes in an entirely unique way) and his talents of Legilimency and Occlumency made him the perfect spy. The fact that he also fooled Voldemort for so many years shows his competency across all areas of magic as well as his impressive bluffing skills. And of course, it was his love for Lily which was his strongest source of magic, even after all that time.