We present a complete catalogue of 27 O VI absorbers at low redshift (0.12 <
z < 0.5) from a blind survey of 16 QSO echelle spectra in the HST/STIS data
archive. These absorbers are identified based only upon matching line profiles
and the expected doublet ratio between the \lambda\lambda 1031, 1037
transitions. Subsequent searches are carried out to identify their associated
transitions. Here we present all relevant absorption properties. By considering
absorption components of different species which are well-aligned in
velocity-space, we derive gas temperatures and non-thermal broadening values,
b_{nt}. We show that in all 16 cases considered the observed line width is
dominated by non-thermal motion and that gas temperatures are well below those
expected for O^5+ in collisional ionization equilibrium. This result reaffirms
previous findings from studies of individual lines of sight, but are at odds
with expectations for a WHIM origin. At least half of the absorbers can be
explained by a simple photoionization model. In addition, in some absorbers we
find evidence for large variation in gas density/metallicity across components
in individual absorbers. Comparisons of multiple associated metal species
further show that under the assumption of the gas being photoionized by the
metagalacitic background radiation field, the absorbing clouds have gas
densities 1\kpc. Finally, we compare our absorber
selection with the results of other independent studies.Comment: 15 pages + lots of figures and tables. ApJS accepte