A few months ago I discussed
cornbread. I slightly modified the recipe to use whole wheat flour instead of white, and due to a mistake in mixing the ingredients, made some further modifications. I've used the same recipe ever since.
A family member is visiting who is sensitive to wheat, so I decided to try an alternative. Instead of 2/3 cup whole wheat flour, I used 2/3 cup whole rye. I also dropped the vital wheat gluten. I didn't make any other modifications (either to ingredients or baking time).

The results were good. The texture is somewhat smoother--rye dough is sticky, and it might be that same quality that transfers into the finished product--and the flavor is slightly different, but certainly okay and in no way inferior to the normal recipe. I was surprised it rose so well. I was expecting it to be more compact.
I'm not sure I'll do this routinely, but it's something to have as an option.