Think of this flirty, flashy option as the "Yeah, baby!" stone, and not only because it was dreamt up in London during the swinging sixties. The arrangement of the gem's many (49 to 144) facets produces a hall-of-mirrors effect. Star Jones's engagement ring boasts a princess diamond.

2-carat princess-cut diamond with side stones (.7 total carats) in platinum, Jeff Cooper, $22,000; at Robbins Bros., 800-610-7464 or robbinsbros.com.