Mariah Carey takes the proverbial cake as far as huge engagement rings are concerned, and come on. Are you really surprised? Nick Cannon put a ring on it in 2009 in a major way, designing a $2.5 million stunner with famed Jacob & Co jewelers. The result was a 17-carat(!) square emerald-cut pink center diamond surrounded by 58 intense pink diamonds and two half-moon diamonds on each side.