Using a tilt lens for a portrait may give interesting results, as it can isolate the eyes in focus, even if not parallel to the camera.
One problem is that available tilt lenses for 35mm are on the short focal length, up to 85mm from Nikon, and that may not be too kind to a full face shot.
I found a good deal for an old Hasselblad Macro 120mm f/4 Zeiss Makro-Planar, which can be used as a tilt/shift lens with one of these adapters, http://www.mirex-adapter.de/tilt_shift_adapter.htm, and others. The macro lens is terrific, and 120mm allows for a nice perspective in a head shot. A similar optical solution is provided at a much higher cost by http://www.hartblei.de/en/sr120m.htm, which I understand uses the same lens.