The following are the reasons why Credit Cards are EVIL, and you should NEVER EVER own one, for your own good and safety.
They Can Buy Goods
Like Food
Clothes
Other Things You Definitely... Probably Didn't Need
They Can Pay Bills
Like Other Credit Cards
Car Payments
Phone Payments
College Tuition (Been There)
They Pay For Gas
More Food
They Boost Your Credit
... If You Pay Your Bill
Or At Least The Minimum
On a serious note, please be responsible. If you are looking at getting a credit card for whatever reason (you want to buy a house, a car, you want to build credit, etc.), make sure that you're paying your bill (and if you can't pay it in its entirety, PAY THE MINIMUM). I know how exciting they seem, but make good choices (even if that means you have to put a cap on how much you can spend) because it's money you have to pay back.