Ovals have been enjoying a high profile since Tom Cruise placed a gorgeous one on Katie Holmes's finger. The cool cousin of the round, the oval shares many of that stone's features, with plenty of sparkle and versatility when it comes to settings. The long shape is especially flattering.

1-carat oval-cut diamond with pave accents in platinum, Cartier, from $17,250; 800-227-8437 or cartier.com for stores.