We report fabrication and characterization of a gas ionization sensor using a sparse array of vertically aligned gold nanorods (AuNR). Our device displayed improved sensitivity compared to the carbon nanotube (CNT) film counterpart, since the room temperature breakdown voltages (Vb) of the tested gases were further reduced. With AuNRs configured as the cathode, Vb was unaffected by gas pressure within a wide range (10-5 < P < 0.1 torr), suggesting that the breakdown process does not follow Townsend's criterion. At higher and lower pressures, Vb increased. The field-emission (FE) and field-ionization (FI) properties of the AuNRs were also studied, and the latter showed measurable pressure dependency in a certain voltage range. The lowering of Vb as well as enhanced FE and FI actions, were attributed to the high field-amplification factor of atomically sharp features on AuNR tips covered by a thin alumina scale.