PSP Lite

Otherwise known as the PSP-2000, or the PSP Slim, released on September 6th, 2007, it is 19% thinner and 33% lighter than the original PSP system (reduced from 23 mm to 18.6 mm and from 280 grams (9.87 ounces) to 189 grams (6.66 ounces))

Also, PlayStation (Sony)'s response to Nintendo releasing the Nintendo DS Lite, a lighter version of the Nintendo DS.