In season four, Arya and the Hound have a tussle with some Lannister soldiers at the Inn at the Crossroads. While the Hound does most of the ass-kicking, Arya kills one of the Lannister soldiers that he leaves injured and alive. Her crazier kill in this scene, though, comes at the end.
Arya finds Polliver, the man who stole Needle and killed her friend Lommy in the process. She recites the exact same words as he said to Lommy: "Something wrong with your leg, boy? Can you walk? Have I got to carry you? . . . Fine little blade. Maybe I'll pick my teeth with it." Then she pushes the needle through his throat.
