Until today I have never seen a backpacker bring a hammer with them. A full on hammer. 
@rbos could be, was using it for tent pegs though.
@andymckay The UBC VOC (Varsity Outdoors Club) had an annual "Kitchen Sink" award for the most unnecessary item carried on a trip.
I did carry a small sledge hammer and crowbar once, but that was for hut demolition and construction.
@rueben those seem like things to carry for a reason 
@andymckay Yah, tools for hut building did not get you a Kitchen Sink award. I recall one year someone won for hauling a 2-burner coleman stove up a mountain unnecessarily.