My family's favorite is wilted baby spinach & browned garlic, with some italian seasonings, mozz and parmesan cheese.
The oddest calzone I've made was with slices of lobster tail. It was awesome tasting, but too moist. The bottom dough was soggy.
I always slit the tops, so there is no chance they will close up. For dough, I just use my NY style dough.
Jack