free gift
An item that one will receive after making a particular purchase. Typically used as a way to motivate one to make the purchase. If you buy that perfume, you'll get a free gift with purchase—this cute makeup bag! I decided to get this after I saw the free gift advertised on the sign next to the display.
free gift
something extra given to you when you buy something else. When you order your magazine subscription, this book is yours to keep as our free gift. This canvas tote is a free gift for everyone who opens an account at our bank today!