Removing push pins from a wall will leave those sprinkled holes that can cause a wall to look horrible. Instead of going to the hardware store and buying expensive caulk and a caulking gun, just buy toothpaste. Go to any cheap store, and buy toothpaste that is the same color as your wall. Use it to fill the holes. Once the toothpaste dries, those holes will be gone.
It's a money saver and a quick fix, especially if you are moving out and hoping to get that security deposit back or don't want to be fined after moving out a dorm room.