The Most Memorable Grey's Anatomy Guest Stars

Michael O'Neill
Episodes: "Sympathy for the Parents," "How Insensitive," "Sanctuary" and "Death and All His Friends"

After his wife is taken off life support at Seattle Grace, Gary Clark (O'Neill) blames Derek, Lexie and Webber for his wife's death. In a fit of rage, he returns to the hospital planning to kill the three of them and any other doctors who get in his way — including Reed and Dr. Percy. After shooting Alex, Owen and Derek — and nearly killing Lexie — he uses his last bullet to commit suicide.