I always thought data storage methods where every state is valid were cool - ie. so that I could feed /dev/random into them and it would spit out something. I

I always thought data storage methods where every state is valid were cool - ie. so that I could feed /dev/random into them and it would spit out something. It's even cooler if every valid output has precisely one encoding. Huffman or arithmetic encoded data is one example of this. And formats that build off that (eg. most video formats) can decode random data as long as you put the right headers on, sometimes making beautiful artwork.