Aluminum foil, adhesive bandages, the ballpoint pen, the computer mouse, the microwave oven -- these are just a few examples of great ideas that became indispensable products we now take for granted.

Nevertheless, of the 520,277 applications that inventors filed with USPTO in 2010, chances are that not even half will be granted patents, and far fewer will become commercial successes [source: USPTO]. For every new gadget that becomes a household name and changes our lives, there are thousands of others that languish in patent office files, unappreciated except perhaps as curiosities. Some of them are ingenious, but plagued with small but fatal flaws. Others are too outlandish to ever gain widespread acceptance. A few are simply ahead of their time.