Kepler-22b
No information is available about the shape of the planet's orbit. Many extrasolar planets are known to move in highly elliptical orbits. We only know that the semi-major axis of its orbit is within its host star's habitable zone. If Kepler-22b has a highly elongated orbit it may well only spend a small fraction of its time within this habitable zone, which would cause extreme temperature differences on the planet and make it inhospitable.