My nipples by far.
My earlobes and neck if kissed in the right way.
My inner thighs can really turn me on if they are gently stroked.
Running a finger gently up my spine excites me and firms my nipples immediately.
Starting from the top, it's my neck and ears, lips and tongue, breasts and nipples (they clearly indicate the situation as they swell and harden respectively lol) and my ass and thighs
Nipples used to be extremly sensitive, but I suspect years of going without a bra most of the time has made somewhat less so. I am told that I can work on them becoming more sensative again, and I believe he was right!!!
Often my inner thigh just above my knee and the backs of my knees.
Check out Kiteares A-Z of kinks and fetishes in micros. The first is of course A Actirasty (if you read it you won't have to google it!)