I've never been a pressie peeker, but other members of my family have been. I've had to come up with a bunch of tricks to make them unidentifiable. For example, a few years ago, my brother got a video for our sister, but no matter how he wrapped it, one shake and you could tell. The reels made a noise. So I suggested he put some loose stones in the box; their noise would hide any identifiable rattle. That worked.
I'd often put random bits of cardboard and stuffing in there too to hide the shape. Especially necessary on CDs and DVDs. I once suspended a gift voucher quite artistically within a K'Nex cube, if I do say so myself....