Movie producer Michael Todd proposed to Elizabeth Taylor with a massive 30-carat diamond ring. The couple married in 1957. Terry Disney/Central Press/Getty
Justin Timberlake proposed to wife Jessica Biel in December 2011 while vacationing in Montana with an 18-carat white gold and black rhodium plated ring. The setting featured two aquamarines on either side, Biel's birthstone. Dimitrios Kambouris/Getty; BJJ/FameFlynet Pictures
Jay-Z proposed to Beyonce with an 18-carat diamond ring; the couple married in 2008. Startraks Photo
Prince William proposed to his longtime girlfriend in 2010 with the same 18-carat sapphire and diamond ring that his father, Prince Charles, gave to his mother, Princess Diana. Samir Hussein/Getty; Arthur Edwards/Getty
Nick Cannon proposed to pop diva Mariah Carey with a stunning 17-carat emerald-cut pink diamond ring surrounded by 58 pink diamonds. The couple married in 2008. Michael Loccisano/FilmMagic
Billion-dollar real-estate mogul Donald Trump proposed to Melania Knauss with a stunning 12-carat ring in 2004. Slaven Vlasic/Getty; Gilbert Carrasquillo/Getty
Justin Theroux proposed to actress Jennifer Aniston in August 2012 with an oval diamond estimated to be between 12 and 18 carats. Eric Charbonneau/WireImage; Justin Thomas/FilmMagic
Prince Rainier III of Monaco proposed to legendary Hollywood beauty Grace Kelly with a 10.5-carat square-cut diamond ring in 1955. Everett Collection; Courtesy of Sotheby's
Brad Pitt proposed to longtime partner Angelina Jolie in April 2012 with a rectangular diamond ring estimated to be more than 10 carats. Steve Granitz/WireImage; PRNewsFoto/The Los Angeles County Museum of Art
Actor Adam Shulman popped the question to Anne Hathaway in 2011 with a 6-carat emerald-cut diamond ring by New York jewelry company Kwiat. Reuters/Mike theiler/Landov; Rex USA