last straw

last straw
    n 1: the final irritation that stretches your patience beyond
         the limit
    

19 Moby Thesaurus words for "last straw":
      causa causans, causa finalis, causal sequence, causing cause,
      efficient cause, final cause, first cause, formal cause,
      immanent cause, immediate cause, occasional cause, provocation,
      proximate cause, remote cause, stand, the last straw, the limit,
      transient cause, ultimate cause