Mistletoe

In Snorri's telling Loki takes the shape of a woman and calls on Frigg, and asks — conversationally — whether everything really swore. Frigg says everything did, except one shoot west of Valhalla, a thing called mistletoe, which seemed too young to ask. That is the whole exploit. Loki pulls it, goes to the assembly, and finds Höðr standing at the edge because he is blind and has nothing to throw. Loki gives him the shaft and guides his aim. Baldr falls, and Snorri says that was the greatest misfortune ever worked among gods and men — and that at first nobody could speak.