Hmm, I do remember Kakashi using a kunai and scroll to save himself... but not for attacking. For killing wise, when Madara thrown it at a fodder ninja and killed him(boss level).
She had the opportunity to use a kunai to destroy Obitos Rinnegan (which would have destroyed Madaras chances of performing Infinite Tsukuyomi and would have also prevented Kaguyas return).... but she still fluffed that up. she just stood there with a kunai in her hand... so useless... why??.....