Abstract: Since 1998 is has been clear that some long-duration gamma-ray bursts come from broad-lined type Ic supernovae -- energetic explosions of bare stellar cores. For bright, variable GRBs observed at cosmological distances, this means that an ultra-relativistic jet must sweep aside the star's envelope before beaming at Earth. However, a much more populous class of dim bursts, which lack evidence for beaming or highly relativistic flow, has recently become apparent. Are these produced by off-axis jets, or shock breakout? I shall review these two physical models, and argue that dim GRBs and related x-ray transients reveal an unexpected diversity of pre-explosion stellar mass loss behavior.