  We show that any direction in the plane occurs as the unique non-expansive
direction of a \mathbb{Z}^{2} action, answering a question of Boyle and Lind.
In the case of rational directions, the subaction obtained is non-trivial. We
also establish that a cellular automaton can have zero Lyapunov exponents and
at the same time act sensitively; and more generally, for any positive real
\theta there is a cellular automaton acting on an appropriate subshift with
\lambda^{+}=-\lambda^{-}=\theta.
