Unused parameter in c++11

You can just omit the parameter names:

int main(int, char *[])
{

    return 0;
}

And in the case of main, you can even omit the parameters altogether:

int main()
{
    // no return implies return 0;
}

See "§ 3.6 Start and Termination" in the C++11 Standard.

There is the <tuple> in C++11, which includes the ready to use std::ignore object, that's allow us to write (very likely without imposing runtime overheads):

void f(int x)
{
    std::ignore = x;
}

I have used a function with an empty body for that purpose:

template <typename T>
void ignore(T &&)
{ }

void f(int a, int b)
{
  ignore(a);
  ignore(b);
  return;
}

I expect any serious compiler to optimize the function call away and it silences warnings for me.