IBM KEYBOARD - http://www.dansdata.com/images/clicky/ballboard1024.jpg
I like the idea of a chocolate keyboard that melts as you type. Each key would have to be cast individually and would take lots of silicone and lots of work. Also it would not last very long. But maybe it will reveal something about which keys people use most depending on which keys melt first.
As the keys start to melt one cannot type using those letters, so one is limited to specific characters and a limited use of language.