For the sake of the scoop, Ben & Jerry's managed to do what no refrigerator manufacturer has: jolt into development the world's most eco-friendly ice-cream freezer. Unveiled for Earth Day 2004 at a Manhattan scoop shop, the chiller relies not on greenhouse gases but on sound waves to keep the precious stuff cold. Research on thermoacoustic refrigeration limped along for 20 years or so until the ice cream duo forked over $600,000 to a Penn State team, which made the prototype in two years.