  We consider a gamma-ray burst (GRB) model based on an anisotropic fireball
with an axisymmetric power-law distribution of the energy per solid angle with
index -k, and allow for the observer's viewing direction being at an arbitrary
angle with respect to the jet axis. This model can reproduce the key features
expected from the conventional on-axis uniform jet models, with the novelty
that the achromatic break time in the broadband afterglow lightcurves
corresponds to the epoch when the relativistic beaming angle is equal to the
viewing angle rather than to the jet half opening angle. If all the GRB
fireballs have such a similar energy distribution form with 1.5 < k < (or \sim)
2, GRBs may be modeled by a quasi-universal beaming configuration, and an
approximately standard energy reservoir. The conclusion also holds for some
other forms of angular energy distributions, such as the Gaussian function.
