This is the most famous knife of Klingons. The D'K Tahg (or Daqtagh). It is the traditional Klingon warrior's knife and consisted of a single, straight-edged primary blade and two curved secondary blades, which are hingedly.
This knife has been specifically made for Star Trek Generations and has a not so edged design than the standard D'K Tahg.
screenshot by movie-screencaps.com (Star Trek - Generations)
The standard Klingon D'K Tahg in the 24th century:
screenshot by trekcore.com (DS9 - Sons and Daughters)