This is my favorite recipe for apple crisp. I'm not sure where it came from, and it is similar to others here, but it is not overly sweet and can be adjusted to your taste in so many ways I can't count. I don't usually recommend any particular variety of ingredients, but in this case, I will make an exception and recommend honeycrisp apples and pecans. It is still good with walnuts or other kinds of nuts, but pecans are the best in my opinion. Honeycrisp apples retain their shape when cooked and are sweet enough on their own to allow for a minimal amount of added sugar. I think this is best served warm with ice cream, but that's entirely up to you.