What counts as "runway in sight" when flying an IFR approach to minimums?
From FAR 91.175:


  (3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
  
  (i) The approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
  
  (ii) The threshold.
  
  (iii) The threshold markings.
  
  (iv) The threshold lights.
  
  (v) The runway end identifier lights.
  
  (vi) The visual approach slope indicator.
  
  (vii) The touchdown zone or touchdown zone markings.
  
  (viii) The touchdown zone lights.
  
  (ix) The runway or runway markings.
  
  (x) The runway lights