  We report discovery of a compact object at high Galactic latitude. The object
was initially identified as a ROSAT All-Sky Survey Bright Source Catalog X-ray
source, 1RXS J141256.0+792204, statistically likely to possess a high X-ray to
optical flux ratio. Further observations using {\em
  Swift}, Gemini-North, and the Chandra X-ray Observatory refined the source
position and confirmed the absence of any optical counterpart to an X-ray to
optical flux ratio of F_X/F_V > 8700 (3 sigma). Interpretation of 1RXS
J141256.0+792204 -- which we have dubbed Calvera -- as a typical X-ray-dim
isolated neutron star would place it at z ~ 5.1 kpc above the Galactic disk --
in the Galactic halo -- implying that it either has an extreme space velocity
(v_z >~ 5100 km s-1) or has failed to cool according to theoretical
predictions. Interpretations as a persistent anomalous X-ray pulsar, or a
``compact central object'' present conflicts with these classes' typical
properties. We conclude the properties of Calvera are most consistent with
those of a nearby (80 to 260 pc) radio pulsar, similar to the radio millisecond
pulsars of 47 Tuc, with further observations required to confirm this
classification. If it is a millisecond pulsar, it has an X-ray flux equal to
the X-ray brightest millisecond pulsar (and so is tied for highest flux); is
the closest northern hemisphere millisecond pulsar; and is potentially the
closest known millisecond pulsar in the sky, making it an interesting target
for X-ray-study, a radio pulsar timing array, and LIGO.
