Floating Point Math in C++ Templates
For a truly evil abuse of C++ template metaprogramming, see this implementation of floating point arithmetic in C++ templates. Apparently it is ridiculously slow to compile (even compared to other C++ code, which is slow to compile to begin with), but beats a hand-coded C floating point implementation in execution speed. C++ is truly a complex and bewildering beast, but definitely powerful in a way that C just isn't.