The lips, obviously.
The forehead? A bit platonic, by human standards, but it has potential. The cheek, the same.
The neck? Hm. It seems a bit more... delicate, shall we say, than I am accustomed to. But one assumes that with increased delicacy comes increased sensitivity, so... yes, I think so.
The shoulders. The torso, perhaps? It all depends on what that uniform is covering - if the hair is as dense there as on the head, I don't think so. If it's more sparse... mm, perhaps.
Now, what about the arms? That patch of skin at the joint that fairly radiates hormones is tempting, but it would be difficult to reach. The back of the hand is, according to the literature, traditionally romantic - but equally traditionally feminine. I don't think he'd appreciate that.
The wrist? Well, it's the other part he uses to manually check the pulse of human patients. With blood vessels so close to the surface, it must be a sensitive region, not unlike the outer edge of a neck- or eyeridge...
He sounds impatient. "Hm?" Also a bit amused; how long have I been staring? "Ah... yes, my dear doctor?"
He scoffs, a derisive little laugh. "Honestly, there are times when I haven't the faintest idea what you're thinking about. Clearly you're not paying attention to me, or your lunch, so what is it?"
So he didn't notice. "My apologies; I was simply... distracted."
"Well, don't let it happen again," he mock-orders, wagging a finger at me. His sleeve slips down, and I can almost see the vessels moving with each heartbeat.
Yes, definitely the wrist.