Someone needs to sticky this topic or something. It seems to come up at least once a week.
Huntington & Newport are the closest. I've never been to Newport. Huntington is nice and has rental shacks where you can rent umbrellas, beach chairs, surf boards, etc. It also has Rubies Diner on the pier which is a cool little 50's restaurant.
By no means is it the closest beach but, on our last trip we visited Santa Monica because it is one of those SC landmarks and had a good time. There is a lot of food options on the pier and of course the carnival operation. The beach is also really nice with a lot of room and good midsize waves/current. There is also a mall about a block from the pier that has a food court for lesser fare food options or shopping.