Have a look at one of this year's obfuscated C contest winners:

This entry weighs in at a magical 4043 bytes (8086 nibbles, 28,301 bits). It manages to implement most of the hardware in a 1980's era IBM-PC using a few hundred fewer bits than the total number of transistors used to implement the original 8086 CPU.

Actual source code, screenshots of it running autocad etc. here.

Some people definitely have too much time and/or too much spare brain power - I'm envious :-)