Heating. Some heaters and hot water systems rely upon natural gas for heating.
Cooking. If you have a gas stove, you'll be igniting natural gas for your stove-top cooking. Barbeques can be hooked up to the mains and consume gas that way.
Fireplaces. Some fireplaces are operated via natural gas, providing an alternate source of heating.
Dryers. You could have a natural-gas clothes dryer, which runs at a higher temperature and dries clothes faster than most electric ones.