The ``equilibrium'' shape of a grain (with fixed volume) embedded in a simple-cubic crystal of the same material and rotated by a small angle with respect to the [001] axis is studied. The dislocation model of grain boundaries of Read and Schockley is used to compute the grain-boundary energy as a function of orientation. The grain shape is then found from this energy via the Wulff construction. Various aspects of the shape are analyzed for different values of both Poisson's ratio \ensuremath{\nu} and a constant characterizing the core energy. One novel feature in this zero-temperature shape is curved portions which meet facets at edges where there is a discontinuity in slope. For small \ensuremath{\nu} the shape is essentially a smoothly curved ellipsoid of revolution with four equivalent elliptical facets on the (100), (010), (1\ifmmode\bar\else\textasciimacron\fi{}00), and (01\ifmmode\bar\else\textasciimacron\fi{}0) planes. For large values of \ensuremath{\nu} two smooth parts can meet at the equatorial plane with a slope discontinuity. In phase-transition language we find, besides first-order transitions, triple points and, in a narrow regime in \ensuremath{\nu}, critical points. Effects of nonzero temperature and the dependence of the core energy on the character of the dislocation are explored qualitatively.