In reply to Klemen:
Some suggestions:
* a chisel, to allow chipping extra holds when in a tight spot (bang the other end with a hex)
* a spanner to tighten loose hangers (salewa or someone already do this, and it's never been useful to me, but perhaps worth mentioning)
* an emergency hanger, for when you find a bolt without one
* nail file, for getting rid of excess growth when on expedition
* a ruler, to measure how deep into a crack a cam has walked, so you can explain to the leader that it's not your fault you didn't retrieve it