A bag (or other container) used to take home uneaten food from a restaurant meal.
A bag used to pick up the droppings of dogs in parks and public places.
A bag (or just a napkin) containing leftovers (like cake or crackers) from a children's party.
A bag containing candy, small toys and other goodies handed out as a thank you gift to guests at a children's party.
A bag containing gifts and promotional material handed out at a conference, exhibition or similar event.