My personal favorite casserole is pineapple cheese casserole. It's become a traditional Thanksgiving dish in my family.
And that is the beauty of a casserole. Often the dishes consist of ingredients that should not mesh, but do in delightful and unexpected ways.
I am from the South, and casseroles are just common courtesy here. Going with your beau to meet his parents? Bring a casserole? Someone died? Send a casserole? Your second cousin just have a baby? Take a casserole. Someone wrestle a bear and end up in the hospital? Growl up a casserole to the family.
I don't care for green bean casserole (I don't like French onions from a can) but I can do some serious damage to a layered Mexican casserole. And what is trifle but a cold dessert casserole in a pretty dish?