Macros

everyone show off your cool macros.  lisp macros, C macros, excel macros whatever

here's my latest

http://pastebin.com/dT4rA3wU

https://github.com/rofl0r/chaos-pp
This is pretty awesome. It was created by the guy who made the Boost preprocessor library but it has more features. It comes with bignums, loops, lambdas, closures, data structures, and more all made out of preprocessor macros.
CHAOS_PP_ARBITRARY_DEMOTE(
  CHAOS_PP_ARBITRARY_DIV(
    CHAOS_PP_ARBITRARY_LITERAL(1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0),
    CHAOS_PP_ARBITRARY_LITERAL(1 7)))
This generates the C integer 58823529411764705882352941.