The first and last product I bought from an infomercial was the Hand-Hammered Wok of China. I still have it and cook with it often, 'bout 15 years later. In fact, just this last Saturday, I made Cashew Chicken with it.
But wait, does QVC count as an infomercial? I've purchased just two items from them. Last one was a great deal on Reed & Barton flatware.