In one year of the International Obfuscated C Coding Contest, there was an entry where the entire program was:
P
With the proviso that you could define P
in the makefile to be whatever program you wanted.
As I recall, it won in one of the categories, and the next year a rule had popped up disallowing that style of entry.
(Edit: six months later or something... I'm sure the "No IOCCC" thing wasn't in the main question when I wrote this...)