Methods and apparatus for percutaneous blood vessel access and tissue tunneling, including guidewire placement, are provided. In one embodiment, an atraumatic distal tip of a tissue tunneling, medical probe is pressed against the derma, and electrical energy (e.g., radio frequency (RF) energy) is conveyed to or from the distal tip to ablate tissue immediately adjacent the distal tip, thereby advancing the probe through the derma while the tissue immediately adjacent the distal tip is ablated. In one embodiment, the medical probe comprises an elongated, rigid, electrically conductive, shaft, and an electrically insulative sheath disposed on the shaft to form an exposed tip electrode configured for electrosurgically ablating solid tissue located immediately axial to the tip electrode to facilitate rapid advancement of the medical probe through solid tissue. The probe may include an axially extending lumen through which an elongated guidewire may be introduced.