m3ph1st0s's programming puzzle 4 (C/C++): “3-way swap”
For 4.4 (14 characters, 1 digit and 4 letters):

int main()
{
  int a = 93;
  int b = 11;
  int c = 22528;

  b&lt;&lt;=a=(c=a)/8;
}


VS2010 with /Wall didn't show any warnings, but I'm still a bit suspicious about using a twice in there (even though it's only modified once).