Here's a futuristic iMac concept with transparent screen and keyboard via Flickr. Who knows maybe one day Apple might make one of these and we will all sell our souls.
that thing is monsterous with such a huge screen size, plus there is no room for a graphics processor or any decent sized motherboard, limiting RAM. and there isnt really any space for a superdrive or USB. the price would also be astronomical. very cool looking, but too much wasted space.