The International Obfuscated C Code Contest
http://www.ioccc.org/
has an annual competion for impossible to read C code
Code:
#include <stdio.h>
#define S(s)char x[]=#s;s
#define Q(x)x
#define A(x,y)y##x
#define B(x,y)A(y,x)
#define C(x,y)B(y,x)
#define Z(s,t,u)case s:if(*p!=32){t;}else{u;}break;
S(B( A( a ,m ),A(n ,i))() {B (A(h,c ),A(r ,a ))*p=x ;B(A( n, i),t)t
=0;B(A(n , i),t)s =0;B( f ,A(r, o )) (;*p;Q( p)++){C( B( A(c,t) ,h),B(A(
w, s),i))( s){ Z( 0,t+=8 *8-00 ,s ++)Z( 1,t+= 8 ;,s++ )Z
( 2, t++ ,putchar(t-73);t=s=0)}}})