Answer: While I can appreciate your wanting to please your partner, I'm afraid that the only way to know the most sensitive spots on his body is to ask him!
The reality is that all men are different. Something that would drive one man to the heights of ecstasy would drive another one insane...and not in a good way. "Most sensitive" might not even be the best thing for which to be shooting. Some men say that certain parts of their bodies are too sensitive to be touched in all but the lightest manner.
That said, the highest concentration of nerve endings on a man's body is on a particular part of his penis (no surprise there!) called the frenulum. This is the small strip of tissue on the underside, just beneath the head. Most men appreciate a well-timed (and placed) lick or tickle on this spot. Just be careful; I know one man who suffered a rather tragic accident when his girlfriend inadvertently got his frenulum caught between her teeth like dental floss!
To be honest, I'm reluctant to go into more detail on this topic because I think that far too many men -- and often their partners -- are way too focused on stimulating their penises. Men need to learn the exquisite pleasures that can be experienced by stimulation of so many other erogenous zones, including the neck, nipples, thighs, ears or really any part of the body. I know it has become a clich, but the biggest erogenous zone, truly, is the brain. Just don't go getting it caught between your teeth!
