Here are a few of the things that are not included in your cruise fare that many guests pay an extra fee for. (this list is not intended to be comprehensive)

Specialty Dining at Restaurants like Chop’s Grill & Giovanni’s Table.
Wifi Package
Soda & Alcoholic Drinks
Port Excursions
Cabanas, Waterpark Access or Hideaway Beach Club access at Perfect Day at Coco Cay