When it comes down to it, FizzBuzz leverages the most basic of programming concepts, including (as Bob Martin tends to put it) Sequence, Selection and Iteration. What you can do is provide a new question, similar to FizzBuzz, but leverage more advanced language concepts for pattern matching. For example, instead of using numbers, perhaps instead you are dealing with a collection of entities, which are polymorphically related. This would allow you to check the candidates knowledge of polymorphism, interfaces, inheritance, etc. For your selection, instead of modulus like traditional FizzBuzz, you could be looking for type matching on the elements.
I'm not sure if this is what you meant by requesting ideas with the same difficulty, but I tried to envision how I might ask this question in an interview.