Chris Allen, a professional yo-yoist, made an enormous yo-yo out of two dog pools. It's 35 inches across, 18 inches wide, and weighs 5.4 pounds. Allen tested it while standing on the roof of parking garage of the National Yo-Yo Museum in Chico, California. At the link, you can watch a video of Allen building and using the yo-yo.
Link via Make | Chris Allen's Website | Screenshot: Make