Well, I once had a problem with enlarged lymph nodes in my groin region.
Knowing that the doctor would have to examine and possibly palpitate the area, I requested a male doctor.
At another time, though, I had a bladder problem and required catheterisation for tests to be conducted. It's extremely painful and suffice to say, it's not something any guy would want to go through. And what's more, the only urologist available at that time was a woman.
And somehow I don't remember any local anaesthetic being used in the procedure.
To those who don't know what catheterisation is, you may way want to read this to understand why I say it's extremely painful and distressing:
http://en.wikipedia.org/wiki/Urinary_catheterization