Sam Tarly, a brother of the Night’s Watch, bravely stabbed a White Walker to protect Gilly and her "little monster" (unnamed in the books, if I recall). Sam's weapon of choice was a dragonglass dagger given to him by Jon Snow from a cache of weapons north of the Wall.
Since the Battle of Dawn, has no one else encountered a White Walker and survived? Has no other character been given the opportunity to try a dragonglass or Valyrian steel weapon?
I use only the books tag, I know in the show Lord Snow killed two (one at Hardhome and one in the wight hunting expedition) and Meera killed one with a dragonglass spear in the Three-Eye Raven cave.