In H&S5 I encountered the "most bizarre" switch statement (8.7.1, p. 277) not using braces.
Here's the sample:

switch (x)
    default:
    if (prime(x))
        case 2: case 3: case 5: case 7:
            process_prime(x);
    else
        case 4: case 6: case 8: case 9: case 10:
            process_composite(x);

The idea seems to be to avoid the overhead of prime(x) for the most common small numbers.

When I saw that statement, I was confused about the missing braces, but checking the official grammar (C1X pre-standard, 6.8.4, p. 147), the syntax was correct: A switch statement just has a statement after the switch expression and the closing parenthesis.

But in my programming practice I never again encountered such a curious switch statement (and I wouldn't want to see any in code that I have to take responsibility for), but I started wondering:

Would any of you know such a switch expression, one without using braces, but still having meaning? Not just switch (i); (which is legal, but a NOP), but using at least two case labels having some sort of useful purpose?