The ones where the camera bursts into flame in your hands, and then a Nikon shooter walks by and points at you and laughs, and steals your girlfriend.
Just the battery not working. You think you have a charged up spare in your bag, and in the middle of something important you change batteries and have no power, because your knockoff was made by some guy earning 6 cents a day in western China. It\'s happened to me, so I just buy the real thing now and have had no problems. Of course, YMMV.