Known as:  Elderberry
Latin Name:  Sambucus spp.
Description: Can cause cynaide poisoning.
Poisonous Parts:  Entire plant.  Plant is cynaogenetic and may contain toxic levels of nitrates.
Symptoms: Drooling, vomiting, diarrhea, swelling around the mouth, difficulty breathing.
Treatment: Unless your cat is unconscious or having convulsions, induce vomiting and initiate procedures to delay absorption and speed elimination.  Get immediate veterinary assistance.

Images courtesy of Brousseau California Flora Photos.