One of the defining signs of when a consumer product is truly preposterous is when its online reviews turn into parody. Take the "BIC For Her" pen, with over 650 snarky reviews on Amazon.
Another equally ridiculous product in an entirely different genre is the Victorio Kitchen Banana Slicer (you know, for the days that are just too hard to slice a banana with a plain old knife). The reviews -- over 250 of them -- include mocking references to it as one of the greatest innovations of all time. There are also mentions of 27 trained monkeys, its power as a marriage saver and so much more.
See some of the best ones here (click "Full Screen" for larger text):