[0x0]

That's neat, but I still think the self-reproducing r.zip from "zip files all the way down" is the best compression trick I've seen:

http://research.swtch.com/zip

[dmit]

There's also dynamic generation of output by specifying a custom filter in a RAR archive that is executed during decompression: http://blog.cmpxchg8b.com/2012/09/fun-with-constrained-progr...