I agree that (void)bla is desirably clear, pithy and unambiguous. And I like something like this if I'm dealing with functions with more than a couple unused parameters:

    static void unused_(int x, ...) { (void)x; }
    #define unused(...) unused_(0, __VA_ARGS__)

This way you can just have one `unused(foo,bar,baz,quux);` line at the top of the function listing all unused parameters.