Every day, a new "you name the product"-killer is launched, so of course there are plenty of examples of copycat or even superior tech products challenging market leaders in their category. But gumption doesn't guarantee success. Contenders that have recently given up the ghost include the Dell Adamo (Dell's MacBook Air wannabe) and the Microsoft Zune media player. Join us for a look at 20 would-be tech killers of the past 10 years and how they fared. Let's start with products that tried to topple Apple equivalents.