At my old job I used to interview would be candidates. We had a great set of interview questions, many of which were created by chikuru. Still I would often try to think of good interview questions on my own. One of my favorites was the following:

What does the following program print?

#include <stdio.h>

void main()
{
   float z = 7.2;
   int i = (int)z;
   int j = *((int*)(&z));

   printf("%d\n%d\n",i,j);
}

It was a good question to ask to see if people understood pointers, casting, and C/C++, but it was a little C/C++ specific.